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Untitled Submarine Short Story

A cup of coffee appeared in the empty space before her eyes, suspended by the rim from the tips of thick fingers. The skin on those fingers was dry, and it cracked in places it circles callous. Each crack was lined in black where years of exposure to various greasy substances had worked its way in.

The cup was made of stamped and rolled metal, the outside coated in a dipped rubber. The rubber coating was also cracked and worn away in places much like the fingers above.

She took the cup and the fingers withdrew from her line of vision. She realized the cup was too hot to be held by anything but the rim or the little handle. She moved it from one hand to the other, holding it by the handle with the ends of her thin fingers, and brought it up to send a pursed-lip cooling breath across the surface. Small chunks of gray creamer that had remained undissolved scattered across the rippling gray liquid.

She sipped at the coffee. It was too hot to have any taste. She set the cup on the shallow wooden sill in front of her, among the thousands of rings that had preceded this particular cup – a pattern that was clearly random yet retained a suggestion of intention. She flipped a metal switch powering up the equipment in front of her and slipped the headphones over her ears.

There was a rush of noise – the microphones were overwhelmed by the sound of the diesel engines that shook the steel walls and penetrated to every corner of the compartment. Her fingertips found the filter switches and volume knobs by rote muscle memory, and she shut down the wash of sound in her ears until the ambient sound in the room from the diesel engines was louder than in her headset. The stack of gauges on the wall in front of her still showed by their quavering needles that the sound detection equipment continued to be overwashed by engine noise. Her eyes scanned the needles for a few seconds, but then silence passed like a wave through the compartment and all the needles dropped down to hover near their zero pins.

The silence was the signal for her to go to work. Her fingertips reversed the settings from a moment ago, and the signal in her headset grew louder as she increased the gain. The sound remained a white-noise hiss, but where the diesel engines had given off a flat and featureless roar, now she could hear an additional spatial quality. The sound expanded around her. She knew from experience that she could hear for miles underwater. And experience had trained her mind to shift into a mode where she understood the particular hiss she now had in her headphones as depth – a huge expanse of a fat column of water in every direction she pointed her microphones.

The sound also had a direction to it. From the surface above came the unique and subtly varying roll and hiss of the waves, which gave her a sense of “up.” And those waves also slid along the hull in a particular way, so her mind knew from the sound alone if the microphones were aimed out to one side or the other of the boat. The bow also created the unique sound of waves cracking and splitting against it. So her ears knew which was was forward as well.

The pads of her fingers rested on the top of the smooth steel curve of the small wheel with its hard little finger-sized bumps molded into it. The wheel controlled the direction the underwater microphones pointed. Outside the boat, the microphones slowly rotated around with the turning of the wheel. She scanned her eyes over the instrumentation – occasionally the electronic indicators could catch a signal before her ears did. But that was rare. Her primary equipment was the headphones. The sounds that came through transmitted a picture of the surrounding water to her. All the gauges and dials were supplemental to the picture in her head, like an engraved image that accompanied the text of a novel.

After a couple of passes, she was sure there was nothing nearby but empty water. Now she engaged some of the electronic filters that did a reasonable job of cutting down the frequencies of the sounds that came from the surface chop. This is where the more sophisticated electronics of the sonar rig could occasionally shine – by filtering out specific frequencies she could focus in on more distant and dimmer sounds. Her ear interpreted the shift in the white-noise hiss of sound as the filters came online as listening further out. Scanning further out meant turning the directional wheel more slowly, since she was covering much greater distances. A careful scan at maximum range could take her ten minutes or more. The biggest challenge was remaining focused on the unchanging sound in her ears. The hovering little signal-strength gauges did help with that by giving her something to look at while searching with her ears. Still, she often closed her eyes and would immerse herself in the slowly-shifting passes of ocean noise. Often it seemed she could feel the long-amplitude heave of the big global swells that passed her by, like giant parents gingerly stepping over small sleeping children in fear of waking them.

She took a sip of her coffee. It barely retained any heat, and now she could taste the caked char of the over-roasted stale coffee grounds spreading like an icing across her tongue, buoyed by the chemical catalyst of the artificial creamer. Those damn metal cups: burn-your-fingers hot when the coffee is first poured, and always cold by the second sip.

With one hand on the directional wheel, she slowly circled the microphones, listening around the boat. Just as she passed to the starboard side of the stern, the slightest extra whir appeared in her headphones. She returned her coffee cup to the sill with its forest of brown rings and curled the fingers of both her hands around grip of the directional wheel.

She closed her eyes and with barely perceptible movements turned back and forth across the bearing where she thought she had heard the whir.

There was nothing.

And then, maybe there was something. Without opening her eyes she moved a hand to flip some switches that enabled and disabled various frequency gains. The hiss in her headphone changed with the switches: fewer higher frequencies, more rushing low notes.

As if sensing something, the control room requested a report from her. “Anything on the sonar Cassandra?”

She did not respond. Not responding to a query from the captain might qualify for insubordination on a military vessel, but for a commercial freight hauler, the sonar operator was a position of some authority, since she was the ears – and the eyes – of the boat.

The wheel slipped between her fingers. Back and forth, inching across the bearing of the signal. The sound there was just strong enough to register on some of the more sensitive gauges, popping the thin black needle up a few ticks each time the microphones rolled over the sound. She picked up a grease pencil and made a mark on the gauge at the point where the signal was at its greatest strength. To her ears it sounded like some kind of distant music, the hum and thrum of an orchestra heard through marble walls and from down a city block. But she knew what the sound really was: a ship.

She slipped one headphone off an ear and leaned back in her chair to call up through the hatch to the control room. “Captain Percy, I’ve got a contact.”

Hemi – he of the thick fingers that had delivered the coffee to her – lowered his meaty body down the steel ladder from the control room and stepped up to the sonar rig. He put the second set of headphones over his ears, and Cassandra turned the directional control wheel back and forth across the bearing of the contact. She pointed to the signal popping up on the indicator gauges. Hemi listened for a minute and then nodded to her. “Alright. Nice work. That signal is barely there. I am sure it is too far off for us to get an accurate distance from the ranging equipment, and too far to see from the lookout ring. But we know what direction to look in. I will speak to Sylvia and see if she wants to re-start the diesels.” He climbed the ladder behind Cassandra, and she could hear him having a conversation with Captain Percy in the control room above.

Cassandra returned her attention to her contact. But it was only a minute before she heard the popping whine of compressed air turning over the diesel engines. She winced and yanked the headset off her ears before the diesels fired and washed out all the ambient noise in both the compartment and her headset.

Hemi came back down the ladder, moving with an agility that would be unexpected in a man of his size, except people working on a submarine were never clumsy. He stood at the foot of the ladder, one foot on the lowest rung. “Sylvia wants to run on diesels to try to out-distance that contact. Her plan is to shut down the diesels every twenty minutes or so, and give you a chance to listen on sonar.”

“Let her know when we lose the contact? Or if they gain on us?”

“That is right. If we do not lose then, see if you can calculate their heading. It would be useful to know if they maintain the same direction as us, or just happened to wander into your sonar range.”

“Alright Hemi.”

Hemi disappeared through the hatch up to the control room.

Cassandra hung her headphones on their peg. She leaned back, crossed her arms, and closed her eyes. There was nothing for her to do until the diesels stopped. She tried to let her mind relax. She tried not to hear the penetrating drone of the diesels. But they were loud enough to make her feel like they had swallowed her whole body. Unlike on a surface ship and some other submarines, the Prospect’s diesels had no direct drive to the propellers. Instead they just acted as huge generators when they were running, charging the boat’s batteries and at the same time generating electricity that powered the huge electric motors that did the actual turning of the props. Due to this configuration, the diesels were set to run at one consistent RPM that was most efficient for generating electricity. This meant that no matter how fast or slow the boat was going, no matter if they were plowing through heavy seas or making good time on a smooth surface, there was never any variation in the pitch or intensity of the engine sound. To Cassandra’s ears they felt like they were just all-on, all the time when they were running. She found it disconcerting to not be able to associate the motion of the boat with the pitch of the engines. The engine noise was also loud enough to make her sonar rig all but useless. She wished there was a way for the submarine to run on just the electric motors all the time. They were nearly silent when powered by battery.

Since darkness had fallen hours ago, the compartment was lit with the red night lighting. The glow of it penetrated through her closed eyelids. Half-dozing in her chair, she imagined the color of the red lights was somehow an exact visual representation of the unchanging drone of the diesel engines. Like she had been entirely enveloped in some hellscape of noise and light.

The thought floated through her dazed mind that she could ask Captain Percy to switch off the lights. But as the thought came up, Hemi was shaking her shoulder and she sat upright. The diesels died away. It was her turn to work again.

The headset went back on. She immediately turned the microphones to the bearing of the sound she had detected earlier. It was still there. Had it changed? Increased in amplitude? Her ears said maybe, but that was based on a memory of the sound from 20 minutes earlier. If it had gotten stronger, the change was still within the wavering variation of the signal-strength needle, which was not registering any further along the graduated scale than before. With a dull pencil nub she scratched out a note on a piece of scrap paper clipped to the sill with her coffee cup. She put down the signal strength and the bearing, and a few cryptic marks of her own private notation about the quality of the sound and what direction she thought it might be headed in. To be thorough, she swung the microphones in a full 360-degree scan around the submarine to make sure there were no other surprise signals popping up out there in the expanse of water she could hear surrounding her.

“Signal unchanged.” She reported upwards to the control room. A moment later the compressed air system hissed and the diesels rolled up to their usual all-engulfing sound. Cassandra returned the sonar headset to its peg and closed her eyes again.

Twenty more minutes passed and she repeated this process. Then another twenty minutes. And another. Each time the signal behind stubbornly refused to change to in any of its characteristics. But the unchanging nature of the sound already told her something. “Signal remains unchanged.” She reported. “Therefore they must be on, or close to, our own course.”

“And you can’t determine range?”

“No. The signal is at the very limits of detectability with sonar. Roughly, that puts the range at something like 12-15 nautical miles.” According to the readings off the gauges, the signal had not changed in the last hour she had been tracking it. Every time she dialed in the contact, the signal strength gauge rose and set itself precisely at the height of her black grease pencil mark. But looking over her notation, Cassandra was seeing something suspicious arising in the more subtle qualities of the sound. She took this last minute of silence before the diesels started again to listen deeply to the signal. To her ear it felt like the sound of powerful engines. And it felt like the prop wash was moving away from her, meaning the ship was moving towards her. No serious sonar operator would claim to be able to hear that kind of detail at the distance she was listening at, but Cassandra felt there were both signal qualities that were empirically verifiable – the stuff detected by the gauges on the wall, the stuff that could be reported to one’s captain – and then there were signal qualities that were understood more intuitively. These were the things that she made her private little marks about.

Her intuition was telling her that this particular signal was following them.

The diesels started again and blew away any further consideration for the time being. It was only a few minutes later when Cassandra heard a mild commotion in the control room above. Captain Percy was shouting questions up to the topside bridge – presumably to Hemi, or whoever else might be up in the lookout ring above the sail. Since the questions were directed upwards, Cassandra could not make out what was being discussed.

The drone of the diesels was suddenly punctuated by the sound of water rushing through the pipes that lined the walls of the sonar compartment she sat in. Cassandra sensed a sinking motion in the boat. Were they diving? The motion was gradual and slight, like descending a gentle hill on a bicycle – not a dive then. After a few seconds of flushing in the pipes, she could hear a change in the sound of the water that ran along the hull. Now it was muted and flowing where previously it had been slapping and rushing with a more chaotic energy.

Hemi’s large boots preceded him back into the sonar compartment. “The lookouts finally got a shadow of your sonar contact in sight against the horizon. Captain Percy is up on the bridge making observations. She was not pleased with the silhouette: it has a militant shape to it.”

“And you lowered the boat to create less of a radar profile?”

“Correct. We are running sail-out now. Though since we are lower in the water, that likely means we lost the visual back over the horizon. The plan is to continue to give you an opportunity to listen every twenty minutes or so.”

Cassandra nodded. Lowering the boat would make it more difficult to track on radar while still allowing them to use the diesels which needed to breathe air to run. The diesels provided much more power and higher speeds than running the electric motors on batteries. But being lower also put more of the diesels engine noise underwater. While they might be harder to track on radar, they may in fact be easier to track by sonar now.

The next time the diesels shut down, Cassandra quickly found the contact and could clearly see that the signal had gained strength – by a small increment, the needle had crept up and hovered just above her grease pencil mark. That meant it had closed some of the distance between them.

“Signal strengthened since last contact.” She reported up to the control room. She used a rag hanging from a hook next to the display to wipe off the old grease pencil mark and scraped a new one onto the signal-strength gauge at the point where the needle now stood quivering. “Still too far to estimate range with any precision.”

The increased signal strength was unfortunate but not unexpected. If the ship behind was tracking them on radar, then seeing the radar signal weaken or disappear would spur them to close the distance to the point where they lost contact. Cassandra no longer had any doubt that they were being pursued.

Speed was not the submarine’s strong suit. If their pursuers were some kind of official or military vessel, they were going to overrun the submarine eventually. If they must lose these pursuers, other tactics would be required. But it was likely Captain Percy was hoping to make it to dawn before employing those tactics.

For the next four hours it was start and stop with the diesels. Cassandra tracked the two vessels in her head from nothing but the sounds in her ears and the marks in her notes and on her gauges. Each time the diesels stopped, Hemi would slide down the ladder, take her readings and mark down the relative positions of the two vessels on the navigation chart. When Cassandra looked at the chart she was pleased to see that Hemi’s marks coincided precisely with what she was holding in her mind’s eye. But as the hash marks marched across the chart, one set closed steadily on the other. There was no question that their pursuers were gaining on them.

“This is unproductive Hemi. We can keep the wheels turning at full RPMs, and they can chase us across the open ocean for days. Eventually they will catch us though, don’t you think?”

“There is no question. Even when ships had sails a sea chase was often just a matter of physics. Two ships rig for their fastest possible speeds, and the faster ship – even if just slightly faster – will eventually win out. It is not like a footrace where there is no telling the endurance of your opponent. In this case it will not even be a matter of days. Look at the arithmetic: if you run out the speed they are gaining on us to its end result, they would catch us before noon tomorrow.”

“But that is where we can take advantage of being a submarine – we have other options we can employ.”

“And because of that we will dive sometime in the next hour, I think. I am sure Captain Percy will want to get under before the dawn light comes up.”

Cassandra was exhausted. The only sleep she had gotten in the last twenty-four hours was her little naps while the diesels were running. That was not the kind of sleep she needed. As soon as the boat submerged she would lose even those little interstitial breaks. She would be expected to give the sonar her full attention.

Two more more of the twenty-minute cycles passed. During each, Cassandra dutifully reported the shortening distance between the Prospect and the following ship. Between listening sessions Hemi came down and told her that the contact had come close enough that from the bridge they could now make out details from the shadow of the superstructure against the horizon. Hemi was certain it was some kind of military enforcer ship – an armed warship of some kind. Hemi was not often wrong about that kind of thing.

“Would you believe they even turned a spotlight on? Played it out over the water, searching for us. Clearly not concerned about us knowing where they are.”

“That’s a terrifying thought. It means they know we’re unarmed.”

“It also means that they do not know precisely where we are – they may only be tracking us with radar not sonar, and maybe having trouble with that. So as soon as we dive we have a good chance of losing them.”

“It also means that they do not know precisely where we are – they may only be tracking us with radar not sonar, and maybe having trouble with that. So as soon as we dive we have a good chance of losing them.”

“The sooner the better then.”

As if Captain Percy had been listening to their conversation, word came down to prepare to dive. The diesels died away one final time to leave the blessed quiet behind them. But not total silence. The subtle hum of the electric motors droned on – still turning the props, but powered by the batteries now.

This was the configuration of the boat that Cassandra was most comfortable with. While running on batteries there was plenty of sonic room for her to listen carefully to the surrounding water. And she knew precisely which filters she liked to apply to drain out the buzzing electric motors from her headset to leave just the swishing and washing sound of the ocean, which she could hear for miles in every direction. At least this was true in every direction except dead astern, where the turning props stirred up enough noise that it clipped off the distance she could hear at more or less the length of the boat.

They had not dived yet though. They were still running on the surface even though they were now powered by the batteries. Apparently Captain Percy was going to make sure everything was in the best order it could be before the boat submerged for the next twelve hours or more while the daylight lasted. This was no emergency dive. They would go down slowly, with deliberation and full control.

But after a few minutes the pipes through the sonar compartment once again were rushing with the sound of thousands of gallons of water passing. This time, without the diesels running, Cassandra could hear the operations of the ship through her headset. She turned the microphones around, listening to the buoyancy and control systems of the boat do their work, making sure everything was happening the way it was supposed to. Mostly this was just a habit to check her hearing acuity. If something went wrong, the system alarms in the control room would probably indicate it before she heard anything amiss.

She could hear the valves at the top of the buoyancy tanks pop open, and the rush of air escaping above the boat as the water flowed into the tanks from underneath. She adjusted the microphones, and could hear the servos steering the dive planes into a downward setting.

The bottom dropped out from under her and the boat sank.

It was only seconds before she heard the valves above the main buoyancy tanks snap closed again – achieving neutral buoyancy only required them to be partially full of water – and the dive plane servos whirred slightly as the boat leveled off at a couple of hundred feet down. For the next few minutes she heard various pumps come on and off and valves opened and closed as Hemi trimmed the boat front to back and side to side by making adjustments to how much water was in the smaller buoyancy tanks that controlled trim.

She focussed her attention on the sounds around the boat rather than the boat itself. The spatial quality she heard around her had changed – it now felt more three-dimensional. She could hear the surface farther away above her head, and the bottomless hole underneath her. Cassandra set her filters to block the noises the Prospect made and circled the microphones around. The water was completely empty. She had lost her contact.

That was impossible though. They were too close to just disappear. They could have stopped their engines, but that didn’t seem likely. She called up to the control room. “Captain Percy, I need you to steer a course that puts our following ship off at an angle. I suspect they are dead astern right now, and I’ve lost them”

“Will do Cassandra.”

She could hear Captain Percy giving muffled instructions to the boys who sat at the rudder controls. And a moment later the boat was swinging to port. As the props swung out of the way Cassandra immediately picked up the contact again.

It was much closer now. She eased the directional control wheel back and forth across the signal. The sound described an image in her head: the pursuing ship, as seen from the underside. She could see the two props of the ship spinning. She could see the relatively shallow draft – it was definitely not some heavy cargo ship displacing a massive amount of water. She could see the bow-wave curled up against both sides of its hull. It was close enough now that she could see the ship’s direction – pointed directly towards her.

“They have increased speed Captain Percy. They are closing much faster now. They are within ten nautical miles.”

“And we’re moving slower now. Give me a report every five minutes Cassandra.”

At the speed the pursuing ship was moving their engines would be making far too much noise to track anything by sonar. Apparently, now that the target they had been tracking with radar had disappeared, they were trying to close the distance as quickly as possible to the last point where they were sure the sub had been. Presumably they would resume their search with sonar when they felt they had a better chance at detection. But the high speed provided the Prospect a short window where their pursuers were essentially blind.

In the headset she could hear the ship on the surface slipping off to her side. She adjusted the directional wheel, keeping the signal strength at its maximum. She had the thought that the ship was turning for some reason. It was a couple of breaths before she reoriented herself and realized that the Prospect was turning, not the contact. Captain Percy was taking the opportunity offered to her by their pursuer’s temporary blindness to make an evasive maneuver and head her boat off in some presumably random direction from where she had submerged.

The situation between the two vessels had changed significantly from the grinding chase they had been engaged in overnight. The distance between them closed quickly now. Within fifteen minutes the pursuing ship was within five nautical miles. With each passing minute, Cassandra could hear more detail and got a clearer picture of their pursuer’s ship – at least of the bottom side of it. They were equipped with a powerful set of engines, and large props shaped for torque and power without much regard for noise. The left propeller was slightly damaged and bubbled in her headset with cavitation. All hallmarks of a warship, or at least of some kind of official vessel tasked with enforcement. Enforcing… what? That was something the bottom side of the ship could not tell Cassandra, no matter how good the resolution of its sounds got.

The signal grew in intensity. The ranging equipment showed a calculation of within two nautical miles now. Cassandra scratched out a number of notes describing the characteristics of the signal and what those characteristics said about the ship that made them. It was often the case that at some future point notes like that could help identify a questionable signal, or provide a useful reference when it came to choosing maneuvers to elude their pursuers.

The sound of the ship’s engines suddenly faded from her ears leaving just the sound of the washing ocean and the hum of the Prospect’s motors. Cassandra watched the needle on the signal strength gauge fall until it was hovering with a slight quiver at only one-tenth the intensity it had been indicating moments before.

“Captain Percy, they’ve slowed dramatically. I estimate they have reduced speed to under five knots.” Cassandra’s report was followed almost immediately by the dwindling away of the Prospect’s electric motors in her headset.

Captain Percy’s voice filled the sonar compartment, amplified over the submarine’s PA as she addressed the whole boat. “Until further notice, keep it fuckin’ quiet if you please. I would like to avoid an encounter with any authority figures today. Thank you.”

Submerged and hovering without the electric motors running granted Cassandra a perfect quiet. This was an opportunity to do some very deep listening. The props of the ship were spinning with slow waving swishes in her headset. One prop was turning more quickly than the other, generating a slightly higher pitch. She put little hash marks down on the scrap paper on the sill in front of her, carefully tracking the ship’s movements. They had begun a slow turn to starboard. That was a good sign, being that it was the opposite direction from the way the Prospect had turned. But it was also possible it was just a short jog to enable the ship to listen behind their propellers and make sure they had not directly overshot the target they were looking for.

In a matter of a few minutes her suspicions were confirmed as she could hear the slosh of the bow wake more clearly. The strength of the signal increased. They put themselves right back on their previous course towards the point where the Prospect had submerged. Now within two nautical miles.

That was when a pulse of energy escaped from the hull of the ship, which Cassandra almost instinctively felt through the feedback of the sonar equipment more than heard. She yanked the headphones off her head and a second later a loud ping resonated off of, and straight through, the hull of the submarine.

There was a minor commotion up in the control room. They apparently had not expected to be pinged.

Active sonar. That resolved any questions about whether the ship was military or civilian. There was no reason for a civilian ship to be equipped with active sonar. It was a tool only for searching for submerged craft. Something that only a vessel with some kind of enforcement mission would have call for.

Cassandra glanced at the ranging gear. It was lit up with the range and bearing of the source of the ping. It automatically engaged whenever it detected a signal as energetic as an active ping.

“1.73 nautical miles, bearing 0-2-5.” She read off the ranging display, loud enough for the control room to hear. Hemi would probably appreciate the precision. Active sonar had the dual properties of both revealing their own location and also giving them precise information on the location of their pursuers.

It was only moments after the ping that Cassandra heard one of the props on the pursuing ship increasing in pitch. She could hear the water pushing with more force off the angled wing of the ship’s rudder. The ship was making a course adjustment. In under a minute she had confirmed its new course as the signal strength increased. The ship had turned away from the spot on the surface where the Prospect had submerged to a new course directly towards the Prospect’s current location underwater. The ping had lit up exactly the spot where they hid.

She reported the ship’s new course to the control room. Two seconds later the Prospect’s electric motors whirred up to a middle pitch that indicated a moderate speed. She felt a mild jolt from the forward acceleration. The contact began a progression across bearings, and Cassandra kept the directional control wheel moving to track it. Captain Percy was turning to a new course to try to keep up evasive maneuvers. The contact soon disappeared directly astern into the noise of the Prospect’s Propellers. Lost in the wash for a minute, it then came out the far side, the low roll of the ship’s engines separating itself from the pulsing white-noise swish of the Prospect’s two props.

Cassandra yanked the headset off her ears as another ping rang the hull of the Prospect.

Evasive maneuvers were going to be useless if there was nothing to restrain their use of active sonar. As if to emphasize that point the pings started to come regularly: every thirty seconds or so. Cassandra now engaged in a nearly continuous battle to protect her hearing. The effort of removing the headphones and replacing them everything thirty seconds with each incoming ping – a gesture that as a single instance was second nature for her – began to weigh heavily on her already exhausted attention. Every ping broke her concentration. It was likely the sonar operator on the ship above knew that and a secondary goal of the timing of the pings was to try to make it more difficult for her to maintain a clear vision in her head of the situation on sonar.

The pitch of the Prospect’s propellers whined a little higher. Captain Percy was putting on more speed. Cassandra estimated by the pitch of the props that they were moving at ten knots or so. If their pursuers also increased speed, their own engine noise would degrade the resolution of the returns from their pings. Active sonar became useless above 15 knots or so. The problem was that the Prospect could only maintain 15 knots submerged for an hour or two before completely depleting their batteries, leaving them dead in the water. At ten knots Captain Percy was trying to split the difference on burning up battery power and sneaking away from the penetrating gaze of the pings.

It was only a matter of a couple of minutes and a handful of further pings before their pursuers also put on more speed so as to not let their quarry slip away. With the increased speed the pinging stopped and as soon as it did Cassandra had to resume tracking the moving contact. Captain Percy executed another turn, and, as always, Cassandra lost the contact as it crossed the stern.

The two vessels again engaged in a struggle of matching capabilities. Cassandra could hear the engines of the following ship rev up as they put on a burst of speed towards the Prospect. The sound of their engines was loud enough to overpower anything else she could hear in her headset, even the sound of the Prospect’s own motors. After ten minutes, their diesels fell back to a pattering churn, and a ping came. The ping was followed by a course-correction to point their bow at the Prospect’s location and then another driving forward of the engines. They repeated this tactic a number of times.

Cassandra had to carefully maintain her track of the contact – back and forth from one ear through her head to the other ear – across a wide range of bearings behind the Prospect as Captain Percy sliced out a zigzag course intended to trip up their pursuers. Things were going in the favor of their pursuers. In under an hour they had closed to within a quarter of a nautical mile of the Prospect. Being that close, the signal from their running engines was so overwhelming that it drove all of Cassandra’s signal gauges up into the far range of their scales.

The next time their engine noise dropped off, Cassandra realized that the Prospect’s own motor noise had disappeared too. Captain Percy had stopped the Prospect and it was hanging suspended in the water column, a couple of hundred feet below the surface. “They’re too close Cassandra. Gonna pause for a moment and see what their next move is.”

Their next move, unsurprisingly, was a ping. Cassandra anticipated its arrival and popped the headset off once again. The ring of it ricocheted around inside the Prospect’s hollow hull.

Cassandra slipped the headphones back over her head and set the directional control wheel to track the contact. Their engine noise wound up. They were moving again. More slowly this time, moving into position nearly over the Prospect’s location.

“Contact moving closer.” It was hardly necessary for her to tell Captain Percy this, the sound of the ship’s screws had becomes clearly audible through the hull of the submarine without the aid of amplification technology. Cassandra pulled the headphones off again and listened to the whirring sound growing louder. The resolution of the sound was exceptional, as it was transmitted through the dense water and resonated by the steel tube of the Prospect’s hull. The ship moved slowly closer until the sound of the propellers indicated that it was directly above them. She could hear the gear disengage, and the engine snapped into idle.

Cassandra’s peripheral vision was caught by the sudden movement of the signal needles on a rarely-used piece of equipment: the ship-to-ship radio. She flipped the switch that piped the sound from the ship-to-ship into her headset.

…To the submerged submarine: You are hereby ordered to surface immediately, open your hatches, and prepare for inspection. This order is given under the authority of the Alliance of Northern Empires…

Cassandra turned her head and called up to the control room. “They’re talking to us on the ship-to-ship!” Captain Percy’s boots almost immediately appeared on the top of the steel ladder from the control room. The toes of her boots hooked around the side rails and slipped down to land with a flat smack on the deck of the sonar compartment. Hemi followed behind, more carefully and deliberately climbing down the ladder rung under rung.

“Put it on the speaker Cassandra.”

Another click of a switch and the transmission from the pursuing ship filled the sonar compartment. Captain Percy’s eyes tracked the bouncing signal needle on the ship-to-ship radio unit.

…tracked you from a port known for contraband logistics. You are suspected of hauling parts that could be utilized as weapons or weapons components by enemies of the Alliance of Northern Empires. If you do not immediately begin surfacing procedures, further measures will be taken against you up to and including the use of deadly force. …Repeating message…

Percy reached over and dialed down the volume on the radio.

“Weapons?” Cassandra asked skeptically, “I thought we were hauling a shipment of wristwatches?”

“Indeed we are.” Said Percy. “Un-fucking-fortunately, the destination for the watches is the Independent Island Pact forces… to be distributed to infantry who need them for timing artillery strikes.”

“Hardly weapons though…”

“Indeed,” put in Hemi, “if they thought we had actual weapons in our hold, they likely would have already fired on us instead of requesting we surface.”

“Doesn’t really matter. We could be hauling blankets and fuckin’ bandaids, if they know our delivery is for their enemies in the Island Pact, they’ll do everything they can to surface us – and then they might try to seize the cargo, maybe our whole boat. We’ll likely end up in non-combatant detention… where at least we won’t be tortured. A fine way to wrap up a career in submarine logistics.”

“What can they do to us if we don’t surface?”

“Depends on how fucking violently inclined they are and what they are armed with.” Said Percy. “Torpedoes, depth bombs – all manner of hell fire within the margins of possibility for raining down on our delicate little heads. And the fuckers know we are unarmed or they wouldn’t have been so free with using that fucking active sonar.”

She stretched the mic from the ship-to-ship radio to her lips and keyed the transmit button. “Ship on the surface, this is submerged sub. Acknowledge receipt of transmission. Please be aware: we are an unarmed cargo vessel hauling consumer goods.”

To submerged submarine: you are ordered to surface for inspection of your cargo by the enforcement authority of the Alliance of Northern Empires, whose sovereign waters we have documented your transiting.

Percy paused, her thumb hanging in the air above the transmit button. “Hemi, start trimming our tanks to make it sound like we’re blowing air into them for surfacing.” Hemi nodded and climbed the ladder to the control room. Percy depressed the transmit button. “Preparing to surface, please stand by.”

Percy reached across Cassandra and put the mic back on its clip. She flipped the switch to disconnect the ship-to-ship unit from the compartment’s PA speakers.

“What are we going to do Captain Percy?”

“We’re going to do what a submarine does best: hide, and then fucking run. Keep an ear on that ship-to-ship and let me know if they have anything new to say for themselves. And we’re going to be going through some maneuvers. Keep a close track on them, and if they do anything fishy, you know where I am.”

“Yes Captain Percy.” Cassandra settled the headset back over her ears as the captain climbed to the control room.

The hiss of compressed air filled her ears in every direction as she turned the microphones around. The high pitch of the moving air was often accompanied by the much lower-pitched sound of rushing water. That was Hemi pushing water around inside the Prospect’s trim tanks. The boat gently dipped forward and back like one of those drinking birds as he moved thousands of pounds of ballast water around. The goal was to leave the boat exactly as trim as before he started, but to make it sound to someone listening on sonar as if they were blowing air in the tanks to gain buoyancy for rising to the surface. Cassandra was sure that was a ruse she would never fall for herself – the accompanying sound of water moving through the boat would tell the careful listener that they were not just blowing in air. Besides, a submarine would have little call for blowing air into the tanks at the depth they were at. In most cases, they would just drive the neutrally-buoyant boat up to the just below the surface, and then blow air in with compressors to fully break above the surface.

But a sonar operator who works on a surface ship might not be as steeped in the finer points of submarine operation as someone who worked underwater daily. Unless they had been well trained specifically for hunting submarines, the sonar operator on the ship above might very well mistake the sounds of lightly blowing tanks for the first moves towards surfacing, buying the Prospect a short window of time.

Cassandra could hear Hemi’s boat-balancing act play out in the water. Air rushed through the pipes that passed near or through the sonar compartment. The sound from the pipes reverberated with the ever-so-slightly delayed sound in the headphones creating the effect in her mind that she was being swallowed up by a gaping maelstrom of air and water.

It did not last long. Hemi only had to blast air a couple of times and then balance the air by returning the water to the tanks it came from. It took a matter of a minute or so before silence made its way back through the boat, paaing in Cassandra’s headphones like a wave from bow to stern. The last little flush of Hemi’s ballast water returned the boat to a dead-even keel.

They hung in the water for just a beat of silent contemplation before the electric motors wound up and hummed along at a low pitch. They slowly pushed forward. Percy was clearly in no rush to move away. As she had told Cassandra: the plan was to hide first, then run. But how was it possible to hide? Cassandra figured they had exactly the amount of time until the sonar operator on the ship above decided to check their location with another ping. There was no reason for that operator to wait: it would likely be a matter of minutes, if not seconds.

Cassandra caught the very short whine of the big servos that controlled the dive planes. That signaled a change in depth: down or up. There was no immediate way to tell from the sound, but she could feel from the angle of the deck that the bow was rising very slightly. So still the ruse. They were indeed very, very slowly climbing towards the surface. The sound of the idling diesel engine above slowly rotated around in her headphones, passing from one ear to the other. The Prospect was turning as if to come about and up to the surface near the point where the ship was stopped. Cassandra kept turning the microphones to track the ship. The idling motor sound was soon nearly directly to the starboard side.

The ping came. Off with the headset, the ringing blast waking Cassandra from her reverie. Even though she knew it was coming it still shook her. The scene in her head – of the ship above, the Prospect’s speed and course, the surrounding empty water – quavered and rippled like she had been gazing at a reflected image in a puddle and someone had dropped a pebble in. It took a minute or two after she returned the headsets and had a look around with the microphones for the scene to settle back into a clear image again.

Just a second after the ping, she heard the servos of the dive planes softly buzz again – a weak signal hopefully missed by the sonar operator above – followed almost immediately by the bow dipping deeply down. She braced herself against the sonar unit, wedging her boots into the angle where the steel of the cabinet met the diamond-plate deck. She pressed her small hands flat against the console, against the pull of gravity. Her chipped-paint fingernails splayed out in front of her. The boat was diving. She waited to hear the flush of water into the forward tanks which typically accompanied a fast dive, but it did not come. It must be that Captain Percy figured the somewhat slower descent of driving down by dive planes alone outweighed the risk of the sonar operator above hearing their big dive tanks flooding and realizing they were not about to surface.

The sound of the contact stopped rotating. Captain Percy had straightened the boat out. Cassandra set the directional control wheel for the microphones at the bearing of the surface ship and then habitually jogged the wheel slightly back and forth, constantly trying to center the strongest part of the signal from their idling engines.

The whine of the Prospect’s electric motors slowly increased in pitch. She followed the rising pitch of the motors both in her headphones and in the compartment as the sound traveled along the hull and jumped across the air to her ear. The boat was picking up speed. The sonar operator on the surface ship was sure to hear that. The question was how their pursuers would interpret an increase in speed.

Cassandra imagined herself on the surface tracking a submarine in the depths. If she had detected it, how would she read a sudden increase in speed? Much depended on the demeanor of the commander of the ship. A suspicious commander might see moving faster as a move to escape. A commander that was more trusting – or more confident in the intimidating power of their weapons – might see it as a typical increase in thrust to gain the surface. Cassandra suspected the latter was more likely. A heavily-armed surface ship normally could expect a cargo sub to surface for inspection since most cargo subs were at least semi-legitimate cargo haulers just trying to complete their deliveries while keeping interactions with authorities to a non-confrontational minimum. Once found and contacted, most cargo subs would surface rather than risk being fired upon. It seemed likely that the experience of this ship’s commander in the past favored the assumption that the Prospect was on its way up. And it now made complete sense that Hemi had not flooded the express dive tanks – combined with more quickly turning props, that would have been a dead giveaway that the Prospect was running. If the only thing the surface ship knew about their movement at the moment was they were going a bit faster, there was plenty of gray-area remaining to give the impression that the sub was rising.

With the increased thrust the Prospect was now gaining depth quickly. Cassandra could hear the idling diesel of the surface ship receding away above and behind her. With every second that passed they were putting more distance between themselves and the surface ship – vertical distance. There was one big advantage submarines had over surface ships, and it was the primary reason those shipping cargo that would be better off not seeing the inspection lights of authorities chose submarines as their means of transport – the capability to move three-dimensionally. The depths offered submarines exponentially more space to maneuver in, something that was enhanced by the fact that many surface ship commanders simply did not have an intuitive understanding of three-dimensional maneuvers. Most surface ship operators conceived of the world as a flat open plane. The submarine commander, at least the good ones, knew the world had depth.

Not just depth, but layers too. The surface operators thought of the ocean as a single undifferentiated bowl of plain water. The sub commander knew water to be the complex medium it is, and that the ocean was made up of a variety forms of water changing with temperature, salinity, concentrations of organic creatures, and currents. And – most importantly to Cassandra – all of these things could affect the way sound travelled through the medium. There were layers far down in the deep ocean where a sound could be transmitted thousands of miles, sometimes right around the sphere of the planet. Towards the surface, things were more mixed where the sun warmed the surface and the cold sometimes pressed up from the deep. This mixing created confusion for a sonar operator. And opportunities for the sneaky sub commander.

As the Prospect gained depth, Cassandra kept the microphones tracking the surface ship’s diesel engine. She soon realized she was not listening so much to the engine noise of the ship as she was to the changing shape of its sound as they put more vertical distance between them. As the makeup of the watery medium changed, the sound that was passing through shifted and mutated. What had been a pulsing rattle when the Prospect was just under the surface became a muted rumble.

Another ping came. The air inside the Prospect’s hull shook with the energy of it. The ruse ended there. The ping would reveal their exact depth and location to the surface ship, and there would no longer be any question that the Prospect was going down, not up.

Almost immediately following the ping – Captain Percy had certainly been anticipating it – the sounds of the electric motors at the stern of the boat fell away and left Cassandra swimming in perfect silence. She observed the sounds of the ocean, the ship above, and the bottomless hole in the depths below. There was nothing to contaminate her signals now. The ship’s diesel continued to slowly fade in her headset as the Prospect silently continued to travel forward and downward under its remaining momentum.

Somewhere far forward Cassandra heard valves snap open and a giant bubble of air burped out of the front of the boat. That would be Hemi flooding the forward tanks to help drive them further down. The bubbling only lasted for a moment before a massive weight of water had flooded up into the forward tanks and the valves shut with a heavy electromagnetic click that pulsed through Cassandra’s headset.

The Prospect continued to drift downwards under just its forward momentum and the extra weight of the water in the bow tanks. The boat no longer generated any sound or signal by which passive sonar systems might track them.

The contact was on the move again in Cassandra’s headset. The Prospect was executing another turn towards some direction that hopefully the surface ship would not anticipate, and the contact was changing position relative to Cassandra.

The spatial quality of the signal was changing more dramatically now as well: an echo came up to her from below, reflecting back the soft rumble from above until at one point it sounded to Cassandra uncannily like somehow there were two ships: one above on the surface and one equally far below in the depths.

A moment later the signal broke up, scattering in a number of different directions, and then dissolved completely in Cassandra’s ears. A space of nothingness passed. Then she scanned the microphones around, and managed to find the ship’s diesels again right on the bearing she lost it. But now it was a far weaker signal, like the ship had suddenly jumped to 20 miles off. The signal barely nudged the dials off their zero pins on the strength gauges.

Cassandra pulled an earpiece off and leaned back. “Captain Percy, I think we passed through a thermocline.”

“Looks like it. The exterior water temperature plot is showing a steep drop. What’s it sound like now?”

“Greatly reduced in strength, diffuse and scattered.”

“With any luck ‘diffuse and scattered’ is exactly how we’ll look to them next time they try to ping us too. Keep at it Cassandra!”

The Prospect was still turning, apparently coming all the way around to something like a reverse course. With the signal constantly rotating around and the ship on the surface floating in a warmer layer of water far above the much colder layer the Prospect now moved through, it was getting difficult to keep the microphones tracking on the signal of the idling diesel engines. Cassandra gripped the steel of the directional control wheel – still propping herself against the angle of the boat, which was starting to ease back towards level – and turned it past the contact till the sound of it faded to almost nothing, and then back while watching the signal strength dials for the highest mark the needles could reach. The sound of distant churning cylinders swelled softly in her headset. Until the Prospect completed its turn, she would have to continually repeat this process to keep the signal in her ears.

When the signal did stop moving through her headset, Cassandra understood the Prospect had used up its reserve of forward momentum and now sat unmoving in the water. She did a full circle with the microphones to make sure she would not be surprised by anything unexpected. As the mics turned passed the bow of the boat she could hear water very softly gurgling. That would be Hemi pushing the excess water in the forward dive tanks overboard – from the soft hiss she guessed he was using only a small amount of pressure from the air system as he tried to stop the boat from sinking while transmitting as little noise as possible. Cassandra hoped he got the Prospect neutrally buoyant quickly – by her estimate they must have already sank deep enough to be near the maximum operating depth of the boat. She was never comfortable when Captain Percy pushed the submarine to its limits. She did not have the faith in the qualities of the aging machines that Captain Percy and Hemi did.

Another rising pulse of energy escaped from the far-off sounding signal as the ship above let loose another ping. This time Cassandra left her headphones on, and closed her eyes as she listened to the chirp splatter against the cold-layer boundary above. The thermocline was bouncing the vast majority of the sound energy back upwards in random directions. But enough of the ping’s energy had permeated the thermocline to reach the Prospect, and Cassandra could still hear it through the hull without the aid of the sonar. It had the quality of someone lightly tapping a tuning fork in the next room. She opened her eyes and the ranging equipment showed a confused set of readings to her.

“Captain Percy, if the signal they are receiving from us is as shaky as what we are getting off them, I doubt they can track us under this thermocline at all.”

“Good. If they lost us, all we have to do is wait them out. And we can stay silent without moving down here for days if we have to.”

Often working on sonar made Cassandra feel like she had a super power: the ability to hear – not just hear but see – through the ocean water for miles and miles in every direction. But that same ability, when it went on for hours and hours without change or new input, made her feel very small in a vast empty space. She did not relish the idea of another 48 hours without sleep tracking a weak signal.

For the next hour the pings came in a more frantically frequent series, sometimes as many as twenty in a minute, like someone tapping on a wall to find the hallow spots. It was clear that the surface ship had lost the Prospect completely. There was desperation in their search method. Between pings Cassandra could hear the slow roll of their engines and when she dialed in the filters just right she could hear the low swish of their turning props.

The ship began a slow search pattern, circling in a widening spiral from the spot where they had lost contact with the Prospect. Because Captain Percy had slipped under the thermocline with the motors stopped the ship above had no hints as to where the Prospect might lay, and so their search pattern had to be thorough.

As time passed, the pings shifted to coming more slowly and regularly. At one point, as far as Cassandra could tell, the ship was directly overhead, and that was nerve-wracking. But it soon continued on its spiraling course. She was thankful that with the protection the thermocline she did not need to remove her headphones every time a ping passed through her equipment. She thought that if she were the sonar operator on that ship, she would switch to listening with passive microphones only. It was clear that the thermocline was reflecting back the high-energy sound waves of the active pinging sonar equipment. The lower-energy casual sounds of the ship seemed to do a better job of making their way through the thermocline. Her advice to the sonar operator on the ship would be to listen quietly for some kind of incidental sound – a dropped tool or a tank trim adjustment. But in her opinion sonar operators on surface ships did not have that intuitive sense for how to search out objects in the expanses of deep water. Since submarines relied on their sonar operators as the only sensory input from outside the boat, they just had a better ability to see the world through sound in the water around the boat. Sonar on surface ships was just another accoutrement. So she was unsurprised that this ship was just banging away uselessly with active pings.

With time, Cassandra relaxed to the point where the pressure to sleep returned. She kept her bleary eyes opened and pinned on the gauges in front of her, and regularly did a full-circle look around the boat – more to keep herself focused than because she expected any surprises to show up in the water.

Hours passed like this. The Prospect lay in a profound hovering silence. There was little movement through the boat. Percy had let her rudderman and planesman go to their racks to sleep. They were less likely to make a mistake that generated the kind of noise that could detected by the ship above if they were asleep in bed than sitting at the boat’s controls with nothing to do. Percy was the only person who remained in the control room.

Cassandra felt like an interred soul. The sounds of the ocean were silent, black, and cold in every direction around her, like a dream of death. Far above a demon circled, searching. Her mind was sliding off bright conciousness as the darkness surrounded her. She knew she was going to lose herself to sleep if she did not do something.

Hemi, with his usual uncanny sense of every aspect of every person and every machine that contributed to the boat’s condition, arrived in the sonar compartment with another cup of coffee for her.

She took it gratefully without a word. He sat down in the seat next to her and put on the second sonar headset. Hemi was an excellent sonar operator himself – he had initially trained Cassandra – so instead of explicitly explaining the situation, Cassandra showed him what was going on by turning the microphone directional control wheel in full circle while Hemi listened, taking in the whole sweep of the ocean just as he had taught her to do.

“Wait Cassandra. What is that sound… towards the bow. Roll back the other way a small amount.”

With two fingers resting on the top of the control wheel she rotated the direction of the underwater mics back until they lined up along the axis of the boat. In her ears she picked up what Hemi had heard. A current of faintly pulsing rapid clicks, carried to her microphones on the underside of the typical swish and swell of active ocean sounds.

“Some kind of regular clicking…”

“I would not judge that a new contact though.”

“No. Maybe something organic… a dolphin or something.” Cassandra took a breath and held it, listening deeply to the delicate and remote sound. The fingers of one hand very lightly turned the directional control wheel back and forth across the bearing of the sound, as always, trying to find the high point. The fingertips of her other hand flipped switches to filter out certain frequencies and adjusted dials to bring up the volume on frequencies that were more closely aligned to the sound. There was no question about its direction: it was perfectly in line with the bow of the boat. It was also extremely faint even with the filters and gain applied. She was impressed the Hemi had caught it.

The sound was an array of clicks. She had indeed heard sounds like that emitted from various cetaceans. But those animals emitted very strong sounds that had direction and purpose. They sprayed clicks all over the ocean, passing the sound back and forth over whatever object or terrain they wanted information about – like someone shining the beam of a light into a dark room. This sound did not move at all. It just radiated like a fixed beacon from some point immediately in front of the boat. It had a rapid beat, and an irregular pattern:

…. …… … …. ….. ……. .. ….. …. …… … …. ….. ……. .. ….. …. …… … …. ….. ……. .. ….. …. …… … …. ….. ……. .. ….. …. …… … …. ….. ……. .. ….. …. …… … …. ….. ……. .. ….. …. …… … …. ….. ……. .. …..

She stopped making adjustments, satisfied that she had isolated the sound to the best of her equipment’s ability. She closed her eyes and set her mind out in the water in front of the boat: where was the sound source located? Despite being very low energy it had a definition and clarity to it that made it feel like it was not distant – it did not sound like it had passed through miles of water. Which made her feel like it had to be something nearby and small, say a swarm of crustaceans or other tiny sea creatures. Or it had to be the boat itself.

“Hemi, I believe that sound is coming from the boat.” She watched his face as he concentrated on the clicks in his headset. She listened for a full minute. The pattern of the clicks remained irregular, presumably random, but it was slowly shifting:

…… ….. …. …… …… …. ….. …. …… ….. …. …… …… …. ….. …. …… ….. …. …… …… …. ….. …. …… ….. …. …… …… …. ….. …. …… ….. …. …… …… …. ….. …. …… ….. …. …… …… …. ….. ….

Hemi lifted his headset from his ears and leaned back to call up to the control room. “Sylvia, you should probably hear this.”

Captain Percy dropped down the ladder from the control room as Hemi flipped the switch to pipe the sound to the loudspeakers in the sonar compartment. Cassandra kept her headset on, preferring the higher definition of the earpieces to the imprecise blare of the loudspeakers.

They listened for a few moments. Percy lit a cigarillo and sucked a long drag on it until the coal glowed, and then exhaled a brown-smelling puff into the already stale air of the sonar compartment. “So what is that Hemi?”

“I know what it is…” said Cassandra. “The wristwatches in the hold. They’re ticking.”

“Can’t fucking be… There’s no way they could be so loud.” She paused. “And they’ve been in those crates for months without being wound. The works can’t start moving by their own fucking selves.”

Hemi continued to listen intently. “No Sylvia… I believe Cassandra is correct. The watches may have been wound up by the motion of the boat… And while a single wristwatch would never be loud enough to be heard, many crates of them could by pure chance have a number of watches begin ticking in alignment – together those ticks could potentially have enough energy to be picked up on the sonar…”

Captain Percy burst. “What are the fucking chances? You would have fuckin’ thought that wristwatches could be counted among the most fuckin’ benign cargoes you could haul, but here we’re being chased across the open fuckin’ sea for a hold full of watches, and the damned watches are down there in the hold apparently fuckin’ conspiring together to give us the fuck away. This is some vengeful wrath-out-of-hell level shit. Like the rules of the game – all strategy and cunning – don’t fucking matter an iota if the evil will of the universe, or its equivalent in callous and arbitrary bad luck, is out to get you!”

“Randomness often aligns into some kind of order.” Said Hemi.

“What do we do?” Cassandra asked.

“Call upon patience and luck.” Said Hemi. “You know order can arise from randomness, but eventually entropy always wins the day and re-asserts itself.”

Cassandra closed her eyes and listened to the ticking. From the position of the passive sonar mics, it sounded like the whole boat was ticking, like a thousand tiny percussionists were down in the hold collaborating together to stir the masses to feel support for some mighty cause through their practiced precision performance. The beats of the thousands of ticking watches were slowly aligning.

….. …. … …. … .. .. .. … … .. .. … . .. …. .. ….. …. ….. . … … … .. .. … … .. .. .. .. .. .. .. .. . … .. . . .

Cassandra watched the signal strength indicator on the sonar unit. With each pulse, its thin needle climbed a little higher. There was some point – she could hardly guess – when it would cross into an amplitude the sonar operator on the ship above them would be able to hear. In Cassandra’s headset the ticking pulsed with an energy that felt like it must be broadcasting out through the water for miles. It was a sound that was centered right in the middle-low frequency ranges that traversed short distances of oceans well, potentially cutting right through the protection of the thermocline above.

. . .

She rotated the directional wheel around to target the surface ship. She focused on the engines of the ship above. They were emitting a growling low frequency that did not vary – the ship was moving very slowly, now searching for the Prospect with their passive sonar instead of the active pinging. Cassandra scratched down a stream of notes marking the speed, direction, and bearing of the ship by tiny increments. When she looked over the marks, they drew the image of an arc in her mind – the current path of the ship’s increasing search spiral.

And then the ship’s engine noise stopped. The image of the arc she was drawing in her mind abruptly reached an end. She jogged the directional wheel back and forth, searching. But there was nothing there. Most likely, they had stopped their engines to clear extraneous sounds for the sonar operator. It made Cassandra feel suddenly very exposed.

. . .

Even with the mics aimed almost behind the boat to try to target the ship on the surface, she could still see the wristwatches ticking in their eerie synchronicity, bouncing the signal strength meter once per second, like a chopping knife slicing up time.

. . .

She kept the microphones pointed towards the last location where she had heard the ship. After a minute of nothing but the nerve-wracking ticking splashing over her senses, she heard a distant electric whine, and then the cough of the ship’s diesels starting up again. Her fingers tightened around the directional wheel. The signal was moving again. She slowly rolled the wheel under her palms. It only took seconds for her to understand that they had turned from their previous course. She tracked them another moment, and then was sure: they had turned towards the Prospect.

“The ship on the surface has started their engines again.” Said Cassandra. She swung the sonar direction over to center on the engine noise.

. . .

In the old days many sailors had been devoutly religious. It made sense: in a world of huge external forces, Cassandra thought to herself, it was helpful to believe that one of those huge forces could be brought over to your side.

“What kind of irony is it that now we need the forces of chaos to save us?” Said Hemi, as if he could hear her thoughts. “I’m pretty sure no old sailor ever called on their god to impose chaos and disorder on their lives to save them from what appeared to be some kind of incredibly unlikely and potentially divine and wrathful order.”

. . . . ..

A discernible second tick suddenly appeared in her headphones, a grace note inserted softly but surely into the silent gap between the strong slices marked out by the needle bouncing on the signal strength gauge.

“That is almost certainly the beginning of the end of it…” Said Hemi.

.. .. .. .. … …

The beats slowly incorporated a chaotic rhythm into their pattern. And as each tick asserted its independence, the signal lost power.

… … . … .. …. ..

“Can you still hear the watches?” Percy Asked.

“No. Not at all.” Said Hemi. “Though that may be largely because Cassandra is tracking the approach of the ship, not our bow with the wristwatches.”

“As she fuckin’ should. What’s the range to the ship Cassandra?”

“Closing fast. Within 500 meters, and engines running at what must be near their maximum… I think they have us.” Cassandra kept turning the directional wheel with enough precision to keep the sound of the ship’s props centered in her ears. The ship was running directly at her. Her eyes locked on the tip of the signal strength needle. It was rapidly rising with the increasing energy of the signal, arcing its way up and over the graduations. And then it stopped climbing and hung there pointing off at an obtuse angle.

The sonar was no longer necessary, the twisted sound of the ship’s props was clearly audible through every compartment in the Prospect.

But it was no longer getting louder. It had leveled off at its maximum. The ship was as close as it was going to come to being directly above the point where the Prospect hung suspended in the deep, and had stopped there.

Cassandra looked at her hands resting on the directional control wheel. The sonar microphones were pointed off to the hard starboard side. “Wait…” Hemi put his heavy hand on her shoulder.

She increased the gain on the sonar. Faintly in her earpieces she heard the splash far above of a pair of heavy objects hitting the water. “They’ve dropped something in the water.”

“Depth bombs.” Hemi said, his other hand pressed against one earpiece of the spare sonar headset.

They both removed their headsets. The three people in the sonar compartment stared blankly at the wall of gauges in front of them, fear widening Hemi and Cassandra’s eyes.

When the explosions came it was a very low frequency double-beat that drummed on the hull of the Prospect.

“They missed.” Cassandra looked at the range calculator. “They were off by hundreds of meters, to starboard. Not even close to our position. That was lucky.”

“You make your own fucking luck in a chaotic fucking world Cassandra.” Said Captain Percy, speaking through the smoke of the cigarillo she had just pulled her lips. “This cold deep water isn’t sitting fucking still. There’s a stiff current here, we drifted. You didn’t feel the boat sliding sideways since we went deep, eh?”

“So much subtlety to that silent movement that I did not even recognize we had moved position. I wonder at my own loss of spatial positioning.” Said Hemi.

Percy sucked again at her cigarillo. “We slipped out of this one – no inspections for us today. It’s just a inevitable matter of waiting it out now. Let me know when they give up trying to kill us and we are well and good out of range. We’ll get the fuck out of here.”

“Sure Captain Percy.” Cassandra put the headset back over her ears and aimed the microphones at the bearing where she knew the ship had been.