Grunt: The Curious Science of Humans at War

12. THAT SINKING FEELING When Things Go Wrong Under the Sea

THERE’S A SOUND THAT water makes, under pressure, when it pushes through a hole too small for its urgency. I know it mainly as a sprinkler sound, a pleasant lawns-in-summer sort of sound. Phhhhhhhh…. To a sailor on a submarine, where there are no lawns and no summer, it’s not pleasant, this sound. It’s the sound of water coming in where it mustn’t. A leaking flange, a ruptured pipe. The ocean with its foot in the door. The deeper you are, the harder it pushes. Three hundred feet down, seawater slams through a two-inch hole with enough force to bend a knee the way knees don’t bend. At a thousand feet, an eight-inch hole lets an Olympic swimming pool on board every three minutes. If it’s not fixed fast, you’re in trouble. You’re sunk.

I’m looking down into a submarine engine room that’s putting out a lot of that sound. Eleven wet necks are bent over leaks—first three, now four. We are 200 feet above sea level, inside a building in Groton, Connecticut, so the risk of drowning is minimal. The room is a mock-up, part of the Naval Submarine School’s Damage Control Trainer, a.k.a. the Wet Trainer, a.k.a. “one of the reasons sailors swear.” I’m on the dry side of a large and very clear (it has wipers!) window that looks in on the engine room and the cursing sailors.

With me at the window is the instructor in charge today, Chief Machinist’s Mate Alan Hough. Every few minutes he gives directions over his shoulder to a colleague at a console manning the leaks, but his main focus is the students. He’s both grading them and giving them feedback. The latter he conveys via signs that he holds up to the window, because no one can hear him through the glass and over the phhhhhhh. TWO PERSONNEL PER LEAK. WORK BEHIND THE PATCH. NO STRAPPING IN THE WATER STREAM. The signs are rigid red plastic, custom-printed by someone who must have wondered.

Today’s subs run on modern technology, but when something goes wrong, the tools sailors turn to may date back to the days of wooden sailing ships. One of the sailors we’re watching uses a simple marlin. Beginning an inch below the hole, he winds a length of thin rope tightly around the pipe, choking the leak one wrap-around at a time. The “pine plug” is just a wood cone, an object more commonly seen in building block sets or geometry classrooms. The tip of the cone is hammered into the hole as far as it will go. As the pine absorbs water, which pine does more greedily than most woods, the cone expands, becoming a snugger fit and a more effective plug.

“Horn,” Hough says over his shoulder. The man at the console blasts an air horn to make the students look up from what they’re doing. Hough grabs a sign (TWO HANDS ON HAMMER) and points at the young man whose hammer and plug the water stream has batted away like a kitten with a yarn ball, or Godzilla with a kitten. This happens nine out of ten times, Hough says; they lose the plug, the hammer, or both. It wastes time when there isn’t any to be wasted. And is dangerous. Ninety pounds per square inch (psi) turns a geometry class learning aid into a “pointed missile hazard.” The sailor retrieves the cone, which is bobbing on the water a few feet behind him. “One good thing about pine,” says Hough. “It does float.”

A hammer does not. “That’s why we tell ’em: hammer of opportunity.” If you lose the hammer, grab what’s at hand. This goes equally for plugs. When al-Qaeda blew a 40-by-60 foot hole in the hull of the USS Cole, the crew stuffed it with anything they could find. “Mattresses, wood, mooring line, sneakers…,” Hough says soberly. “Wrapped it up and shoved it in the hole.” It took three days, but they got the flooding under control.

I had met Hough earlier in his office, which he shares with two other men. A jar of Smucker’s Goober Grape stood out for the stripey, colorful whimsy it brought to the ill green-beige that someone, at some point, decided to paint the US military. Hough is rangy and pale-complected. He has an appealing overbite that, as he speaks, causes his incisors to touch down on his lower lip like children jumping on a bed. He was raised in a region of the country where people use “them” as an indicator rather than “those.” But Hough is nobody’s goober. He can take apart a steam turbine faster than most people can put a name to it.

Everything else in today’s leak-stopping arsenal is classed as a patch. The term is apt, but misleadingly unintimidating. This isn’t like patching a pair of pants. It’s like patching a riot hose while the water’s still on. You can’t come down on the rupture from above. The patch has to be slid over it from the side, like a blanket over a trash-can fire, and then cinched tight.

Hough watches a pair of sailors fail to secure a medium-sized patch called a strongback. The strapping they’re using is designed to hold up to water pressure as high as 6,000 psi. “So, for water at 90 psi to be leaking out, that’s a very bad job they’ve done.” The red plastic sign Hough would like to hold up does not exist: UNFUCK YOURSELVES.

Hough is tough on his students because the Wet Trainer is a kiddie pool compared to the reality it represents. Here was the situation on the USS Squalus, 50 feet down, after a 31-inch air-induction valve failed to close on a test dive in 1939. “The sea had found its way into the maze of pipes that ran the length of the Squalus. In the control room, jets of salt water sprayed from a dozen different places.” I’m quoting Peter Maas’s account of the sinking in The Terrible Hours. “The men worked frantically… seizing hold of whatever they could to stay upright.” And then the lights went out.

And this is from the submarine patrol report of the final patrol of the USS Tang, October 24, 1944, the day one of her own torpedoes broached the sea’s surface, curved sharply left, and blew a hole in her stern: “The Tang sank by the stern much as you would drop a pendulum suspended in a horizontal position.” A Lieutenant Lawrence Savadkin described the scene: “With the sudden downward angle of the boat, men and loose gear were bumping and falling by me with the rush of water.” The sub school Wet Trainer doesn’t tilt, but the one at the Officer Training Command in Rhode Island, nicknamed the USS Buttercup, does. (Apparently quite dramatically. “You never save the Buttercup,” Hough says.) With the understated monotone that comes of hindsight and report-writing, Savadkin concluded, “Confusion was great at this time.”

In extreme scenarios like these, the crew skips patches and plugs and heads to the watertight doors. Separating the three or four watertight compartments of a submarine are great, thick round hatches that, in appearance and penetrability, fall someplace between the door of a bank vault and that of a front-loading washing machine. Everything behind the door may fill, but the flooding stops there. Depending on how much sea has been taken on, an “emergency blow” may be ordered. A blast of pressurized air empties the submarine’s ballast tanks like a Heimlich maneuver on a purpling guest. The hope is that this lightening and hollowing of the stricken vessel will counter the weight of the floodwater and float it to the surface.

“If you can’t get enough bubble, you’re going down.” This from Jerry Lamb, technical director at the Naval Submarine Medical Research Laboratory (NSMRL), a few buildings over from the Damage Control Trainer. I’ve left behind Alan Hough and his sopping sailors to meet with Lamb and one of his counterparts from the UK’s Royal Navy, Surgeon Commander John Clarke. Both are well versed in the sequel to damage control: submarine escape and rescue.

Lamb pours me coffee, and Clarke goes off to find milk. He’s back a minute later, squinting at the date stamp. “Jan 20. Should be okay.”

“What year?” Jerry Lamb is a droll, upbeat soul, his essential good cheer yellowed but slightly by two and a half decades with the Navy. The Navy: smart people, dumb bureaucracy. Meetings, paperwork, conferences. A moment ago I heard Lamb refer to something called the “missile defense luncheon.” I pictured doilies under water pitchers and PowerPoints of incoming warheads. Who could eat?

Neither the Tang nor the Squalus could get enough bubble. The first order of business for a sub on the floor of the sea is to alert potential rescuers. Then, as now, each submarine compartment is equipped with mini launch tubes for flares, smoke signals, location buoys. On World War II–era subs, the location buoy was a sort of floating phone booth in the middle of the ocean. “Submarine Sunk Here,” read the sign on the Squalus buoy. “Telephone Inside.” It was like a New Yorker cartoon that didn’t quite make sense. There needed to be a third line: “No, really.” A length of cable connected the buoy to the downed sub. When a rescue vessel arrived, its crew would haul the thing aboard and reach inside for the phone. Peter Maas recounts this moment in his book. The rescue vessel’s commanding officer, Warren Wilkin, takes the receiver and opens with a breezy “What’s your trouble?” Like he’d pulled up alongside a car on the side of the road with its hood propped open.

The commanding officer of the Squalus—here, too, seemingly unflurried in the face of catastrophe—comes back with a chipper “Hello, Wilkie.” Whereupon a swell lifts Wilkin’s boat and snaps the cable, leaving all further communications to be hammered out in Morse code on the hull of the sub.

Technology has of course advanced since the 1940s. The modern location buoy, SEPIRB (Submarine Emergency Position Indicating Radio Beacon), sends a coded message via satellite with the sub’s ID and whereabouts to the closest rescue coordination center. The buoys are still launched through the little tube, though, and ideally that tube hasn’t been welded shut, as it was on some cold war–era subs—to keep the buoy from launching accidently and revealing the sub’s position to the Soviet subs upon which it was spying. Before a location buoy is launched, someone takes a grease pencil and writes all over it, as much detail as there’s room for: damage to the sub (and crew), air quality on board, etc.

What happens next depends on how dire the situation is. Inside every US sub is a fat, white three-ring binder labeled “Disabled Submarine Survival Guide,” and in the front of that is a stay-or-go diagram: a decision tree of yes-or-no questions. Is the flooding contained? Are all fires out? If so, if the situation is stable, the answer will likely be Stay. Wait for the rescue vehicle. In water less than 600 feet deep, it may be possible to get out of a sunken sub and make one’s way to the surface—Hello, Wilkie!—however, for reasons we’ll shortly get to, this is a last resort.

A US sub is stocked with enough oxygen-generating and carbon dioxide–subtracting capability to last at least a week without power: a week of what Clarke calls “bottom survivability.” By bottom he means the ocean floor, but the British accent, to my ear, anyhow, tilts it toward the naughty meaning. Which kind of fits: bottom as in, “your ass,” will it be saved? Seven days is meant to be the outside limit of how long it should take for help to arrive. Fifteen countries and NATO have submarine rescue systems—deep submergence vehicles with decompression capabilities—but they differ in how deep they’re able to go. None is designed to function deeper than 2,000 feet; then again, neither are most submarines. (Modern US submarine “crush depths” are classified[54] information, but educated speculation puts them in the neighborhood of a half-mile down.)

Clarke adds that there may be well more than seven days of supplies. “Because you’re probably dealing with a proportion of the crew.” It took me a moment to realize what he was saying. He was saying that the oxygen will probably hold out longer than a week, because some of the crew won’t be using any. Aboard the Squalus, twenty-six men drowned in the first few minutes of the disaster, entombed in the flooding compartment when the watertight doors closed.

The least of anyone’s worries is starvation. Subs leave port stocked with full provisions, much of it in cans—so many cans, in fact, that they may overflow the storeroom on the smaller class of subs, with the result that entire passageways, in the early weeks of an underway, are cobblestoned by cans. Water may be a concern, if the desalination unit isn’t functioning. The Disabled Submarine Survival Guide includes unflinching water conservation strategies. “Minimize water closet ops following bowel movements to one minimal flushing cycle… every three uses.” To control odors, the Guide recommends covering the mess with the powder used by the galley crew to mix the “bug juice.” The high acidity of the drink is pointed out, leading one to assume that that’s why it’s used for this, though it’s also possible it’s an editorial comment on bug juice.[55]

And then you wait. The men of the Squalus huddled disconsolately on the torpedo room floor, eating canned pineapple. It is notable that neither crew, Squalus nor Tang, exhibited panic. Aboard the Tang, the commanding officer wrote in his report, “No one was hysterical or disorderly at any time…. Toward the last, conversation seemed to be mostly about their families and loved ones.” One of the last messages tapped out by the crew on the hull of the sub S-4, accidently rammed and sunk in 1927, was “Please hurry.” The laborious and time-consuming inclusion of “please” breaks my heart. It’s so Navy: courteous and respectful to the end.

The crew of the Squalus were as lucky as they were unlucky; the Navy’s first submarine rescue chamber had just been completed and tested. The Squalus was its maiden rescue. Thirty-three survivors rode it to the surface. The chamber was a modified diving bell. As with an inverted drinking glass lowered into water, the pressure of the air trapped inside keeps the water outside. A diver accompanied the bell to position its opening over the lip of one of the submarine’s hatches and bolt it in place. The sub’s hatch could now be opened, and small groups of crew helped into the chamber.

Prior to this, sinking was likely a death sentence. Even a few inches of water will bear down on a submarine hatch—or a car door, for that matter—with sufficient pressure that it can’t be pushed open (unless one equalizes the pressure by letting water in). On the smaller subs of the 1920s, the air would last about three days. It was one of these “iron coffins,” the S-51, that inspired Lieutenant Commander Charles “Swede” Momsen to come up with a way to get people out. Momsen’s sub had been the one that first arrived on the scene. All the crew could do was stare at the oil slick on the surface of the water, “utterly helpless,” as Momsen wrote to a friend. When the sub was salvaged, bodies of the crew were said to have been found with their fingers torn and bloodied from trying to pry open a hatch against fifteen tons of ocean.

Given that most US ballistic missile submarines today spend the bulk of their time in oceans that bottom out deeper than their crush depth, the term “iron coffin” has regained some accuracy. Crush depth is the point at which the hull succumbs to the extreme water pressure and the sub implodes. John Clarke likens it to putting a submarine inside a giant bomb. The sub shatters inward. And the crew? “If you can imagine,” Clarke says, “all the metal parts are imploding together and anything in the way would be crushed and shredded and pounded into bits.” No one saves your bottom now. On April 10, 1963, the USS Thresher imploded, killing all 129 men aboard. “She’s scattered all over the seafloor,” Jerry Lamb says.

In light of the deep-sea haunts of modern subs, why even bother with rescue and escape systems? Do they simply exist to, as one submariner expressed it, “give moms and dads a warm feeling”? No, no more so than airplane emergency exit slides. Because, as with airplanes, most collisions take place on arriving or departing: in port or airport, where the traffic is busiest but the plummet most survivable.

The Tang went down in water just 180 feet deep, but rescue was complicated by the circumstances of battle. She sank in the midst of the convoy of Japanese ships she’d spent the night torpedoing and sinking. In the end, bad air forced the crew’s hand. Smoke had built up from the burning of classified paperwork, and saltwater had reached the batteries, creating deadly chlorine gas. Disaster luncheon. You didn’t need a decision tree to know that Stay had turned into Go.

Swede Momsen invented something for this scenario, too. During World War II, subs were equipped with escape trunks and Momsen lungs. (The “lung” was a wearable air supply that, upon reaching the surface, handily converted to a flotation device). Like an airlock on a spaceship, the escape trunk allows for the equalization of pressure inside and outside. On a sub, this allows the hatch to be popped open and the lung-clad sailor set loose in the brine. The Tang was the first bottomed sub from which sailors escaped without the aid of a rescue bell. There were nine, four of whom subsequently drowned or disappeared. (In the surreal etiquette of war, the five survivors were plucked from the near-freezing water by their enemies—as the Tang’s commanding officer described them, “the burned and mutilated survivors of our own handiwork”—who then beat them and sent them to starve in a prisoner of war camp.)

What happened to the rest of the men gathered in the Tang’s torpedo room in their Momsen lungs? Why didn’t they escape? They weren’t sure how to do it. “A majority of the men,” reads the patrol report, “had never been properly trained in the use of the Momsen lungs or operation of the escape tank. They, therefore, didn’t have any self-confidence in their ability to escape, causing a general feeling of defeat among them…. After the first two attempts there were very few men left who cared to try an escape although they knew what was going to happen to them below.” They are all there in the Summary of Escapes. Torpedoman’s Mate Fluker: “Would not try after this, his second attempt.” Unnamed Ensign: “Removed in stupor from trunk; preferred not to try again.” Unnamed Machinist’s Mate: “Would not try after this, his first attempt.”

A little practice might have made the difference. “Although everyone had read how to escape,” says the report, “not one had actually went through the motions.” In 1930, at the urging of Swede Momsen, an escape training tank was commissioned for the submarine base in Groton. With the hope that every submariner would have a chance to went through the motions.

AT 40 feet deep and 84,000 gallons, the Naval Submarine School’s Pressurized Submarine Escape Trainer holds easily as much water as a hotel swimming pool. In diameter, though, it’s closer to a Jacuzzi. It’s the sort of thing you might drop into by accident, like a manhole, because you didn’t notice it was there. Despite the aquamarine water and the echoey tile walls, pool isn’t the right word. This is a column of pretend ocean that exists for a single, highly nonrecreational purpose: to practice bailing out of a stricken sub.

Twenty-six sub school students stand around the water’s perimeter in identical (Navy) blue swim trunks. They are young enough that the pimples on their backs still outnumber the tattoos. In ten years it will be different. Navy boys accrue ink like sun damage. A little more every year, in every port. The first training exercise will begin in an escape trunk that feeds into the water fifteen feet down. No breathing apparatus will be worn, just a life jacket. The instructor calls it “a buoyant exhaling ascent,” a term I will tuck away for later use should I ever be called upon to write opera reviews.

Exhaling is the word to be underscored. Faced with an ascent from deep underwater, novice swimmers are inclined to hold their breath—not just to stay alive, but to help buoy them to the surface. They may not realize that that initial lungful of air they took in will expand as they rise and the water pressure decreases. If that breath expands enough, it will burst the lung’s alveoli—the tiny sacs where an exchange of gases in the air and the blood takes place. Should this happen, air bubbles can get into the bloodstream. Air embolism. Not good. Critical care luncheon. The bubble can act like a clot, blocking blood flow and starving organs of oxygen. If the organ in question is the brain or heart, the tissue damage may be fatal. There is speculation in the Tang patrol report that this had been the fate of four men who made it out of the escape trunk but then disappeared: that they’d lost the mouthpieces of their Momsen lungs and hadn’t realized the consequences of holding their breath.

“It’s the Golden Rule of sub school,” the instructor, Eric Nabors, is saying. “Don’t hold your breath.” Nabors carries the evocative title Diving Officer, and seems built in keeping. His hair is buzzed to a half millimeter, his wedding band tattooed. Nothing disrupts the hydrodynamic flow of Eric Nabors in a wetsuit.

To modulate their exhalation—not too fast, not too slow—the young men are instructed to pretend they’re blowing out birthday candles. Yelling also works. To further discourage breath-holding, Nabors and his fellow instructors used to inflate a wine bag down at the bottom of the water and let it go. As it surfaced, the bag would burst.

While Nabors and I have been chatting, I’ve referred to the wine bag as a bota bag. Nabors finally stops me. “What are you saying?”

Did I have the wrong term? That goatskin pouch that herders used to sling over one shoulder? In Spain? The kind where you open your mouth and squirt in the wine?

Nabors blinks at me. “I’m talking about the bag from wine-in-a-box.”

My escort for the day has been chatting with Nabors, and I notice she calls him “Jim.” This would explain the Jim Nabors album (Kiss Me Goodbye) mounted on his office wall, but not the ID badge, which says “Eric Nabors.”

“I fought that battle for a long time,” he says when I bring it up. When your last name is Nabors, there will be people who call you Jim, no matter what you do to discourage them. “Eventually I gave up.”

The bursting bag has been replaced by a video of itself, because the real thing was too intimidating, and no one wanted to get in the Escape Trainer afterward. Few of the students will cop to it, but there’s some anxiety in the house today. Some of these boys can barely swim. The Navy entrance requirement is minimal. You are dropped in a pool fifty feet from the edge, and you get to that edge however you can. You don’t have to like water to join the Navy. “I don’t even like baths,” said one submariner I met.

Nabors explains to the students the sequence of events. A pair of divers are with each student up to the time he begins his ascent, to be sure he’s exhaling at the right rate, that he’s been able to clear his ears, that he’s not feeling panicked. Then they let him go. It’s over in a few seconds. “You’re going to pop out of the water, and a diver is going to say, ‘Are you okay?’” Nabors says. “And you’re going to shout your name, your rank, and ‘I’m okay!’” (So the guy standing by with the clipboard can put a check next to the name.) “Got it?”

“Yes, sir!”

A few minutes later, the first student pops out of the water, buoyant with air and relief. A diver is there to receive him and steer him to the edge. If you wandered onto the scene without knowing where you were, you might think, baptism?

“Are you okay?” shouts the diver.

“Yeah.” Nabors and the clipboard guy exchange a look. Kids today.

One student backs out of the ascent. You can tell who he is by the red bathrobe; everyone else’s is tan or blue. This isn’t done to shame him; no one but the staff knows the significance of being “red-robed.” It’s a way to alert them to keep a watchful eye out, in case a medical issue develops. In this case, the boy was just scared. He confesses a fear of drowning. I glance at his bare feet for the traditional Navy “anti-drowning tattoos”: permanent inkings of a pig and a chicken, one on each foot. Because when the old frigates sank, pigs and chickens from the ship’s hold could be seen floating on the water’s surface.

The boy’s fellow students were sympathetic, and this he expected: “One team, one fight.” I’ve heard the word brotherhood applied to submariners. At 7 percent of the Navy, it’s a tight-knit community. Especially boat by boat. Where an aircraft carrier crew may number 6,000, US submarines have room for fewer than 200. There’s an intimacy born of not only the diminished personal space that the smaller classes of subs impose but the months-long isolation and, until recently, the absence of women. “There’s a lot of hugging and stroking heads,” a former NSMRL psychologist told me. “I was taken aback by how physically affectionate they are.”

Inevitably, this has fueled rumors. Andrew Karam, author of Rig Ship for Ultra Quiet, told me about sitting in a bar with his shipmates when a “skimmer”—a surface sailor—walked in. “When he realized we were all submariners, he said, ‘I know about you guys. Hundred forty men go down, and seventy couples come back up.’”

“That’s not true,” Karam deadpanned. “We have some threesomes.”

The US Submarine Force began integrating female officers in 2010, with enlisted ranks following in 2016. So far, so good. Jerry Lamb says a recent ban on cigarettes provoked more clatter. And then this happened: The day before my visit, Navy Times broke the story that female officers on the USS Wyoming had been filmed in the shower.

I ask Nabors whether he has to tell his students not to urinate in the Escape Trainer.

“It’s not even a topic of discussion. It happens.”

I forgot he’s a diver. I’m told divers pee in their wetsuits. Me, I’ve never. “I can’t even pee in the ocean.”

The guy with the clipboard glances at Nabors. Wow, the glance says. Live a little.

THE STUDENTS troop single file to the stairwell, ducklings in a row. They are going down to the bottom of the Escape Trainer for the big ascent, the 37-footer. This time they’ll wear a SEIE (Submarine Escape and Immersion Equipment) suit, a partially inflatable head-and-face-encompassing zip-up that attracts unwanted comparisons to a body bag. Like its more minimal predecessors the Momsen lung and the Steinke hood, the SEIE suit incorporates an air supply and openings to vent excess air as it expands on the ascent. This allows the escapee to breathe normally and not have to worry about bursting lung parts. Students practiced the “exhaling ascent” earlier so they’d know what to do if there was a problem with the escape suits. Something like this, for example: “The rubber was cracked and tacky and most of them were stuck together.” This is Andrew Karam in an email to me, describing the Steinke hoods he was asked to inventory for an underway in the late 1990s.

“On the bright side,” Karam went on, “we spent almost all our time in water more than a thousand feet deep, so opportunities to use them were few and far between.” The maximum depth at which a Steinke hood has been successfully tested is 450 feet. The greatest depth at which a SEIE suit can be counted on to save you is 600 feet. That is really all you need ask for, because if you’re escaping into water deeper than 600 feet, you’re likely to be killed by decompression sickness no matter what outfit you have on.

To understand decompression sickness (the bends), it’s useful to think about one of those countertop carbonation units. Bubbly water is tap water with the bends. When you force pressurized gas into a container with liquid in it—be that container a SodaStream bottle or a scuba diver—some of that gas may go into the liquid. (To get all jargony, the gas goes “into solution” for the greater cause of equilibrium.) Now say the pressure in the container lets up suddenly—because the bottle has been opened or the diver has swum up toward the surface. Those gas molecules that had been forced by the air pressure into the liquid will now come back out of solution. (Here again: seeking equilibrium.) As they do this, the gas molecules link together in the form of bubbles. Never mind why. They just do. Now you have a glass of refreshing fizzy water, or a looming case of the bends. The bends is bubbles migrating through the body and causing problems: acting like a clot and disrupting the flow of blood to vital organs, or pushing apart tissue and causing pain, or both, and more.

Divers can avoid the bends by ascending slowly. This gives the body a chance to simply exhale the gas as it comes out of the blood and into the lungs. (Nitrogen is the main culprit; air contains a lot of it, and it likes to dissolve and hide in fat.) The more time a diver has spent breathing pressurized air, and/or the more highly pressurized the air, the more nitrogen she’ll need to dump and the slower, therefore, she’d need to ascend.

Decompression may or may not pose a danger to escaping submariners. If they’re lucky, the air inside the stricken sub has remained as it was when they left port: pressurized to sea level. In that case, submariners can usually escape with little danger of the bends. But if the vessel floods, the water that’s come on board will compress the air like a trash compactor. Now the sailors are like scuba divers: They’re breathing pressurized air, and some of the gases in that air will be pushed into their blood and tissues. Depending on how long they breathe this air and how compressed it is, they may, like a diver, need to decompress in order to ascend to the surface safely. Breathing the pressurized air in the escape trunk for the minute or so that one is inside it isn’t enough time to create a problem unless one is down very deep. At, say, 800 feet, the air in the escape trunk would have to be so highly pressurized (to equalize with the outside pressure and allow the hatch to open) that breathing it for even a minute would force enough nitrogen into the body to put one at risk for the bends.

At the far, nightmare extreme of the bends is something called explosive decompression. On November 5, 1983, four divers were relaxing in a decompression chamber on the deck of an oil rig in the North Sea. For reasons that remain unclear, one of the dive tenders opened the hatch, reducing the pressure in the chamber from what it would be at 305 feet underwater to what it is at sea level—in a fraction of a second. Nitrogen bubbled out of solution instantly, in the men’s brains, their blood, their fat and muscles. The pathologists wrote in the case report that the men’s fat looked like “sizzling butter on a frying pan.” They surmised that the blood had begun to bubble instantly, “leading to an instantaneous and complete stop of the circulation.”

Diver four had been at the hatch when it blew. Good-bye, Wilkie. He was the champagne at the top of the bottle. The pathologists speculated that in addition to the breakage caused by being shot through the partially open hatch, he “also must have exploded.” He arrived at the autopsy suite in four plastic bags. Some of his organs were missing, having been “blown straight into the sea.” Like the gases in the abdominal cavity, air in the brain pan had also expanded in an explosive manner. “The scalp, with long blond hair, was present but the top of the skull and the brain were missing.”

I’ve been looking through a porthole at the bottom of the Escape Trainer. Watching this scene, the rag doll movements of the divers and the silvery jellyfish air bubble that floats from the hatch in a languid blurp, it is easy to forget the murderousness of deep water. Submariners can’t afford to forget. Mistakes can so swiftly give rise to disaster, and then where are you? Too deep for help or escape.

The risks are amplified when someone on your crew has been up for sixty hours. It has been an enduring unease of the military that the last people you’d want operating subs or fighter jets or automatic weapons are often the ones doing it: the persistently, catastrophically sleep-deprived.