Sheck Exley

Under Pressure

Scuba had finally come full circle: from the first explorers who strapped on archaic tanks back in the 1950s to technical divers who now strapped on underwater computers and dive to depths so great the pressure could crush a car faster than a five-car pileup.

By Jerry Shine

In an underwater cave somewhere beneath Mexico, two divers, Sheck Exley and Jim Bowden, are squeezing through a narrow crevice toward a light ahead. The light comes from an opening, an entrance into a second cave known as Zacatón, whose abyssal depths almost defy description.

Exley and Bowden pass through the opening, then rise to the water’s surface 25 feet above, emerging into a circular pool surrounded on all sides by rocky walls that reach up through the water 70 feet into the air. The stark beauty of Zacatón’s cliffs, sun-baked and baron, is breathtaking but the divers’ true interest lies at its bottom, 1,080 feet down.

Bowden, a 54-year-old Texan whose hair and beard have long since turned an ivory white, has devoted much of his life to exploring underwater caves such as this throughout Central America and Mexico. In this part of the world, if it’s underground and underwater, he’s probably been there. Caves are his love and his life, and just about every penny he earns is poured into them. Anything left over at the end of the month he uses to take care of the more mundane things, like his electric bill.

Bowden’s partner, Exley, is universally regarded as the Michael Jordan of cave diving. An exceedingly open man to those he knows, intensely private to those he doesn’t, Exley is an enigma in the diving world: he holds virtually every cave-diving record (in terms of depth and penetration), yet he wants no publicity for those records. His average build belies the tough martial arts workouts he puts himself through daily to prepare for the rigors of his obsession. Rigors he knows well. At 45, he’s spent more time in underwater caves than most fish. His passion for these caves is legendary, but beyond that he has a supreme, natural ability to operate within their confines. Most divers, even highly trained ones, lose a certain percentage of their land skills once they dip beneath the water’s surface. Not Exley. His transition from one medium to the next is as effortless as it is complete – over the course of some 3,000 dives, he’s worked his way out of enough life-threatening situations to give Jacques Cousteau an inferiority complex.

Exley is also something of a reluctant standard-bearer for the new sport of technical diving: a subculture of mission-oriented divers who use technology to plunge to ungodly depths. Unlike the typical recreational diver who spends his free time dreaming of vacations in the Caribbean, technical divers are more likely to be found searching the Internet for information on diving computers, heads-up displays, rebreathers, and portable recompression chambers. They use complex software to plan their descents, carry US$10,000 to $15,000 worth of equipment with them into the water, and place themselves in situations well beyond the capabilities of the average recreational diver.

At first glance, they may seem possessed of potentially fatal amounts of testosterone. But, in the last few years, their ranks have mapped out some of the world’s deepest underwater caves and descended on such previously undiveable wrecks as the Monitor and the Lusitania.

No technical diver, however, not even Exley, has reached the depths of Zacatón, where hydrostatic pressure hits 487 pounds per square inch (compared with 14.7 pounds per square inch at sea level). Pressure this great can implode even the best diving equipment as easily as you could crush a styrofoam cup.

Its effects on the body can be just as dramatic, making the range of physiological barriers read like an inventory of hyperbaric nightmares: decompression illness (a k a the bends), oxygen toxicity, high-pressure nervous syndrome, deep-water blackout, and nitrogen narcosis. Any of these can result from breathing air or other gases under extreme pressure. To combat these dangers, Exley and Bowden have spent the last year going over every detail of the dive, attempting to make it, if not safe, at least survivable.

It’s April 1994. Their dive plan is fairly straightforward: each diver will drop down into the near-vertical cave under the weight of 200 pounds of gear, maintaining visual contact with the weighted line anchored to the bottom.

At these depths, the inert gases in their breathing mixtures will be rapidly absorbed into their bloodstreams. Water pressure will keep those gases compressed in the form of small, harmless bubbles – that is, until the divers return to the surface.

If they ascend too quickly, the decreasing water pressure will cause the gases to bubble up out of the solution like a can of soda shaken before being opened.

The result is the bends: an excruciatingly painful, often fatal, condition.

To avoid this, Exley and Bowden, after touching the bottom, will rise to the surface slowly, making “decompression stops” at predetermined depths for specific periods of time; this will allow the gases to come out of the solution gradually. The entire process will keep them underwater for more than 10 hours.

The key is a speedy descent. The faster they reach the bottom and then start back up again, the less gas is absorbed. To that end, they’ll drop at a rate of 100 feet per minute. Put into perspective, a commercial diver descending to 1,000-plus feet would breathe through a surface-supplied hose and take upward of 24 hours to reach his destination. Exley and Bowden will be there in 12 minutes.

Another problem is air supply. Because divers can’t carry 10 hours’ worth of gas on their backs, dozens of extra tanks – each holding a different mixture designed to speed decompression – are tied into the two descent lines at the various decompression stops. Even with these extra tanks, however, if either diver takes more than six breaths per minute at any point during the descent, he’ll run out of gas long before making it back to the surface.

The late morning sun is cresting over the ridge surrounding Zacatón as Exley and Bowden complete their equipment check. They’re ready. One last nod to each other and under they go, heading down, down, and down some more through mineralized sulfur clouds held in suspension, through warm water growing ever darker. At 230 feet, they maneuver around a ledge and all light fades to black. Flashlights now cut through the darkness. Minutes pass. Hurtling downward silently, Bowden checks his pressure gauge at 850 feet and suddenly realizes he’s used up his breathing mix much faster than expected. There’s no time to figure out why. He may have enough to reach the bottom, but not enough to make it back up. To continue on would be suicide. It may already be too late.

He begins inflating his buoyancy compensator – the “BC” is a collapsible vest used to control buoyancy – but momentum and the 200 pounds of equipment he’s wearing carry him deeper. He sails past the 900-foot mark. To kick or swim would be fatal at this depth; the carbon dioxide generated by the exertion would cause an almost instant blackout. He can do nothing but hit his BC – and hard. Finally, he reaches out to grab the line; as the 925-foot mark slips through his fingers, he comes to a stop. Little by little, the inflator begins lifting him back up through the darkness and eventually into water broken by sunlight. He sees Exley’s descent line 25 feet away. He also sees Exley’s staged decompression tanks tied into it, waiting for him. But he doesn’t see Exley.

The men and women who pioneered the sport of scuba diving in the 1950s were hard-ass explorers in every sense of the word. The technology was new. Its limitations, and those of the human body while using it, were largely unknown. Early divers pushed these limitations as far as they could, and then some. Within 30 years, they could be pushed no more: scuba experts were reaching depths in excess of 300 feet.

It was physiologically impossible to go much deeper breathing air. At such depths, nitrogen – otherwise harmless – transforms into a mind-numbing narcotic. Oxygen, too, becomes toxic, poisoning the central nervous system and sending the body into convulsions. The only way to go deeper is to add varying amounts of other inert gases – helium, hydrogen, or neon – into the mix.

The stumbling block was decompression. Since these other inert gases are absorbed into the body at rates different from nitrogen, the standard sport-diving decompression tables – schedules of decompression stops which allow safe absorption of the different gases to avoid the bends – didn’t apply. And there were no alternative mixed-gas tables. That left divers with two choices: stick with air and dive no deeper than current limits, or take a chance using mixed gas and a homemade decompression schedule.

The chance was not a small one. It is critical that divers use the right mix of gases, in sufficient quantity, at the correct time and depth. Even minor decompression mistakes can be deadly, and using mixed gas was akin to a game of Russian roulette.

In the spring of 1988, six years before the Zacatón dive, Sheck Exley entered Nacimiento del Rio Mante, an underwater cave in Mexico, with four huge tanks containing a mixture of helium, nitrogen, and oxygen strapped to his back and sides.

(He would use 21 tanks and 11 different gases in all.) Exley had already made several mixed-gas dives over the last year, but this was the first one he would make with a decompression schedule developed specifically for him.

“We were so far off the charts (in terms of depth and duration) that we were going on gut feeling,” remembers Bill Hamilton, editor of Pressure, the Undersea and Hyperbaric Medical Society newsletter, who developed the dive plan for Exley. “The computer would spit out numbers but we couldn’t take them at face value – they weren’t based on actual exposures,” he recalls. “So we manipulated them, worked around them, interpolated between them – you know, all the things you’re not supposed to do – and, eventually, we got a dive plan out of them.”

From previous, shallower dives, Exley already knew the hazards of Mante. Silt, which if disturbed could obliterate visibility for hours, lined the cave floor, while the jagged edges of the cave wall jutted out from each side. Strong, upward currents slowed his descent to 30 feet per minute.

As he went down, the cave’s shape began to hourglass – growing wider then narrower then wider again – while maintaining its near-vertical drop. His goal was to dive beyond 700 feet, deeper than any scuba diver had been before.

Twenty minutes later, Exley passed below the 700-foot mark, even as the narcotic effects of the nitrogen crowded his senses. Suddenly, an explosion behind his head knocked him almost unconscious. He steadied himself against the wall of the cave and tried, without luck, to locate the problem.

He checked his depth gauge. He was now at 780 feet. Whatever the explosion was, it was time to head back. He rose quickly into shallow water (shallow being a relative term) and began his decompression, breathing from tanks he had staged along the way, each of which contained the precise gas mixture registered on Hamilton’s decompression schedule.

Timing was essential. To linger too long, or not long enough, at any one stop would be an open invitation to the bends, so he kept a close eye on all three of his watches. Wearing three watches was a habit he’d picked up the year before when he lost his only watch mid-dive; this forced him to count off each decompression stop in his head. One-one-thousand, two-one-thousand, three-one-thousand…. Luckily, he had to do it for only a couple of hours.

And the explosion? A Plexiglass case housing the motorcycle battery that powered his flashlight had imploded. It just couldn’t take the pressure.

Would you venture out into the unknown out of greed? Greed works only in the world of ordinary affairs. To venture into the terrible loneliness, one must have something greater than greed. Love. One needs love for life, for intrigue, for mystery. One needs unquenching curiosity and guts galore.

With that somewhat purple prose from Carlos Castenada’s The Fire from Within, Michael Menduno, a former marketing executive going through a mid-life crisis, launched aquaCorps, a dive magazine with an attitude, in 1990.

Until that moment, in the 40-plus years since Jacques Cousteau had introduced the world to the scuba tank and underwater adventure, diving had steadily evolved from the province of exploration to that of a tame, organized activity, generating millions of dollars on the sale of equipment and travel vacations. New diving rules, established by training agencies and bolstered by dive magazines (the sport’s new power structure), were set in stone in the 1960s: never dive deeper than 130 feet, never dive alone, never get into decompression situations.

The sport of rugged individualism, of Lloyd Bridges on the old TV show Sea Hunt, soon had an accident rate lower than that of bowling. All vestiges of the bad old days, of explorers diving by the seat of their wet-suit pants, were stricken from the record; people entering the sport had no idea that things were ever done any other way.

Michael Menduno’s aquaCorps took a different approach. Its standard fare included mixed gases, improved decompression methods, treatment strategies for the bends, and fatality reporting – topics that no other magazine had touched in decades. In one fell swoop, all those divers your mother warned you about now had a pulpit from which to preach.

“People who were already into deep diving and mixed gases grabbed it up,” says Menduno. “But the powers that be, well, they were a little cautious.”

A little apoplectic would be a better description. Angry, almost hysterical, editorials filled the pages of other dive magazines. Manufacturers of some types of mixed-gas equipment were banned from the industry’s annual trade conference, to be reinstated later only under the threat of legal action.

By the time the second issue of aquaCorps hit the stands, Menduno had christened the unnamed sport “technical diving.” Even as he did, it became clear that it was far less forgiving than its gentler predecessor. In the summer of 1992, eight divers in the US died during deep or mixed-gas dives. There were other deaths in Europe.

Nevertheless, the tide had turned. The allure of exploring virgin and near-virgin caves, wrecks, and reefs, all the while pushing personal limits to the edge, testing them, extending them, was too powerful to ignore. Training agencies for technical diving were being established. aquaCorps launched tek, an annual conference that began drawing divers from around the world. Even the more mainstream dive magazines were touching on previously taboo technical-diving topics. And as more deep, mixed-gas dives were conducted, data on their limits were accumulated and disseminated, eliminating some of the old dangers as newer ones beckoned.

By 1993, the growth of technical diving vaulted Sheck Exley to legendary status. “He was walking on the dark side of the moon compared with everyone else,” says Bret Gilliam, a longtime friend of Exley and CEO of Technical Diving International. “When he made his original Mante dive, not only did he go deeper than anyone had gone before, but his first decompression stop was deeper than anyone had ever been.” Among technical divers, it was becoming clear that Sheck Exley was The Man.

In the summer of ’93, he used a decompression schedule developed with his own software to dive a South African water-filled sinkhole called Bushmansgat. Squeezing through a 3-foot crack to enter it, he picked up speed and descended 200 feet into the world’s largest underwater cavern. Even to Exley, its size was overwhelming.

He continued down, at a rate faster than ever before. At 700 feet, however, Exley’s body lodged a severe protest. Hundreds of small concentric circles, each with a sparkling dot at its center, filled his vision. His body began itching and stinging. It was high-pressure nervous syndrome, a little-understood phenomenon brought on by severe, rapid compression. The extreme pressure inhibits the function of the brain, causing neural circuits to run wild. Exley had never experienced it before.

He hovered at 750 feet, to consider his options: abort or continue down. Decision made. He started down again, more slowly this time, though there was little physical change. By the time the cave bottomed out at 863 feet, Exley’s entire body had begun shaking uncontrollably.

Exley ignored it. His flashlight cut through the darkness. Even without full vision, he could make out what appeared to be a lunar landscape: a uniformly flat bottom, sloping away from him, covered with small rocks, and buried in nearly a foot of black sediment. No one before him had ever stood where he was standing.

He couldn’t stay long, since every minute of extra time he spent at that depth would eventually have to be paid for with extra hours of decompression. After a good look around, he inflated his BC and began to rise. He was more than halfway to the surface before the syndrome subsided.

At Zacatón, 100 feet beneath the water’s surface, Jim Bowden hovers at his decompression stop. Above him, the sun has set below the ridge surrounding the cave.

A support diver moves in close and begins gesturing to him. As she does, the silent motions of her fingers weave a message that he already knows in his heart but has tried not to believe. Sheck Exley, the man who read paperback novels underwater to pass the time during long decompression stops, the man who celebrated New Year’s Eve for the last 25 years in dozens of underwater caves throughout Florida and who rescued countless other divers from near-fatal situations, has not come up. Sheck Exley is dead.

Bowden continues to hover. He can’t head back down for Exley; he doesn’t have the gas supply. He can’t surface; to do so without finishing his decompression would be certain death. He can only wait, locked into the silence of a diver underwater, suspended in decompression, mourning his friend.

“That was a horrible moment,” remembers Bowden. “We knew the risks we were taking, but still, it was hard to imagine Sheck not surviving the dive – not surviving any dive.”

Within hours, reports of Exley’s death go out over the news wires. aquaCorps’s office is swamped with e-mail. The rec.scuba site on the Net fills up fast, as do all the scuba bulletin boards. The thought of Exley not returning from a cave dive (even one to 1,080 feet) is as incomprehensible as the idea of a young Muhammad Ali dying in the ring from a punch. “To find out that he was mortal came as quite a shock to a lot of people,” says Gilliam.

No one expected Exley’s body to be recovered from the depths of Zacatón – who could go down to retrieve it? – but several days later, his descent line, heavy with unused decompression tanks, is winched up, and his body, wrapped into it, is recovered. An autopsy is inconclusive; with no witnesses, it’s impossible to know what happened during the dive.

The most likely scenario is that, like Bowden and for unknown reasons, he used up his gas much faster than expected. Unlike Bowden, however, he mustn’t have realized this until too late. At that point, without enough gas to inflate his BC and rise, he wrapped himself into the line to stop his descent and to give himself time to think.

He was most likely experiencing flashes of narcosis as well as another episode of high-pressure nervous syndrome. When he ran out of gas mixed for that depth, he switched to another that could be breathed safely only much closer to the surface. At that point, he must have suffered an oxygen convulsion, lost consciousness, and died.

At the ’95 tek conference in San Francisco, Exley’s ex-wife and longtime dive partner accepts a posthumous award in his honor. Other than that, there’s little mention of his death. Maybe the topic has been talked out. Maybe it’s time refusing to stand still.