As if the problems of nitrogen narcosis and oxygen toxicity were not enough to deal with, divers also noted that when they breathed helium mixtures they felt incredibly cold and they worried about the possibility of life-threatening hypothermia. Helium is an excellent conductor of heat, and sport divers concluded they were losing heat both during breathing and through the skin, which was surrounded by a thin layer of water between the body and the rubber wetsuit—called that because it allows water to enter. Most divers used wetsuits in the relatively warm water of Florida’s caves, and heat loss was not a problem when they were breathing normal compressed air. To overcome their perceived heat loss when they breathed helium gases, sport divers wore a drysuit, which was watertight and used as insulation a combination of underwear resembling a ski suit and a gas, usually air. Even with a drysuit, though, divers breathing helium mixtures noticed that they felt cold. The culprit was at first thought to be the insulating gas itself. Divers would inflate their drysuits when they were already underwater, and if they were breathing a helium mixture, they used this gas to inflate their drysuits. Instead of insulating, it felt as if the helium mix had the opposite effect because of helium’s high heat conductivity. The solution was to pump a different gas—compressed air or even argon, a heavy gas that is an excellent insulator—into the dry-suit, but this meant adding yet another compressed-gas bottle to the diver’s equipment load.
With all of the complications entailed in breathing mixed gases, Exley kept on diving using only compressed air. But then, in 1981, the German diver Jochen Hasenmayer, using mixed gas, succeeded in diving down to 476 feet in a French cave, shattering Exley’s cave-diving depth record by over 100 feet.
Ever competitive and willing to revise his own beliefs, Exley decided that the path to greater depths could now be safely negotiated using mixed gases. Hasenmayer had obviously worked out the various complications of mixed-gas diving. Exley wrote to Hasenmayer, and the two became friends, sharing information and even diving together. In 1983 Hasenmayer managed a mixed-gas cave dive to 656 feet; it would take Exley until 1987 to best his friend’s efforts. By 1989, Exley had again set the world deep-scuba-diving record when he descended to 867 feet inside Mante, a cave in Mexico that plummeted downward at a slight angle to depths unknown. Many who knew him well observed that Exley seemed obsessed with holding the deep-cave-diving record, and with beating Hasenmayer in their friendly rivalry.
The Rouses had taken the mixed-gas diving course with Exley two months before I met them at Steve Berman’s. At the time I myself was preparing to take Exley’s course. Whenever I hung out at Fort Rouse, they bubbled with excitement about the experience of learning from and diving with the master. The Rouses had been impressed with Exley, Chrissy especially so: “The guy’s amazing in the water, and he’s in such great shape,” he said to me when we discussed cave divers at camp. “He swims so fast all the time! Like a human torpedo. Man, it was an effort to keep up with him.”
During the class, the Rouses had learned both the theories and the practical aspects of mixed-gas diving, including how to calculate ideal gas mixtures for a given depth, and how a gas should be mixed. Trimix, for example, contained three gases, typically oxygen, helium, and nitrogen. In order to brew trimix, the diver needed only to put the correct amount of helium into an empty scuba tank, and then top it off with air, which naturally contained the two other required gases, oxygen and nitrogen. For the gas called nitrox, an oxygen-nitrogen mixture, the diver only needed to put in a given amount of pure oxygen in an empty scuba tank, and then top it off with air.
Exley emphasized hands-on experience. In addition to the classroom lectures, students learned how to mix their own gases. Chris remarked to me later, “It was weird to see that Sheck doesn’t believe in checking the mix with an analyzer. He says that if all the gauges you’re using are good, and your mathematical formula is right, then the mix will come out right.” I too was surprised to hear this, because I knew that divers who were doing mixed-gas diving held it as gospel that after mixing a gas, you should analyze the oxygen content. Exley, who had a degree in mathematics and taught the subject in a Florida high school when he wasn’t diving, was confident of his formulas.
Chrissy was impressed as much by Sheck’s aquatic style of living as he was with the man himself: “It’s cool. Imagine living in a double-wide trailer with dive gear all over the place and a cave in your backyard!” Exley lived in Live Oak, and there was an entrance to Cathedral Canyon cave behind his house. Chrissy added, “He’s even got a hot-water hose set up.” The hose piped hot water down as far as 20 feet into the spring, where the diver had to rest so as not to surface too quickly.
Sue, overhearing the conversation from inside the camper, yelled out, “Hey, Chrissy, tell Bernie how you two dummies didn’t listen to Sheck and how you wish you had. Go on, tell him!” Chrissy’s face sank into chagrin for a moment. “Oh, okay, Mom,” he mumbled. “Sheck told us not to wear drysuits when we went into Cathedral cave, but Dad and I did, figuring we’d be cold if we didn’t. Mom took his advice. We didn’t know about the hot-water hose until the end of the dive, and Sheck and Mom were taking turns putting the hose down their wetsuits to warm themselves up. Dad and I did get a little cold in our drysuits because we didn’t have heavy underwear on, and of course we couldn’t use the hose in our suits.” I heard Sue laughing from the camper.
All divers have to contend with other problems besides cold, narcosis, and toxicity. The greatest and most enduring problem divers face—one still not fully understood—is decompression sickness. Decompression sickness is caused by the body’s inability during an ascent to remove all of the biologically inert gas—nitrogen, in the case of divers breathing compressed air—that it absorbs while breathing underwater. On the ascent, the excess inert gas emerges from the tissues to be expelled during exhalations. If the body cannot eliminate the gas fast enough through breathing, the gas forms bubbles in the bloodstream, which press on nerve endings and can block the flow of blood; this stops oxygen from getting to parts of the body and causes injury to those areas. It is extremely painful; the common term for decompression sickness, the bends, refers to the contortions of victims in agony as a result of pain in the joints and muscles.
If a diver comes up slowly from a dive and stops at different depths for various lengths of time, the body has the chance to eliminate the excess gas before bubbles form. Severe cases of the bends can cause the victim to experience numbness in certain parts of the body, or even to lose bodily functions such as eyesight, hearing, clear speech, bladder or bowel control, sexual function, and even life itself. Getting bent is no laughing matter. Although methods of treating decompression sickness have been around for some time, an understanding of exactly what happens to the body during treatment is still elusive.
From the time that human beings first began to penetrate deep waters, many observers felt that depth quests would lead to nothing but tragedy and that sport divers would never be able to handle extremely deep dives. Sadly, Jochen Hasenmayer fell victim to an operational problem while diving in the 200-foot depth range in a European lake; he could not stop his diving suit from inflating with insulating gas, making him look like a lethally buoyant balloon with arms, legs, and a small head. He shot uncontrollably upward and broke the surface like a cartoon-character missile. Hasenmayer was rushed to the hospital in severe pain, crippled by decompression sickness. Medical treatment in a recompression chamber—a small tubular machine typically no longer than a car, in which the diver is put under increased pressure, simulating diving depth, and slowly brought back to surface pressure—failed to alleviate his paralysis, though it may well have saved his life. He will spend the rest of his days in a wheelchair.
Long before the arrival of sport diving, human beings have been stirred by curiosity and driven by economics to explore what lies beneath the surface of the waters of the seas, rivers, flooded quarries, and caves, and to retrieve what we have lost beneath the water. Not being ab
le to see under the waves led the human imagination to conjure all sorts of beasts lying in wait to trick, or even devour, those who entered a seemingly forbidden realm. But there have always been people who ventured into the deep despite the superstitions. Depending on your philosophy, they were either brave, foolish, or insane.
For those who have never been underwater before, “deep” is definitely a relative term. Already within just 20 or 30 feet of the surface can be found another world, now familiar to us via television and still images, as well as elaborate private and public aquariums. But all of this was completely unknown until fairly recently. Ventures into the deep were once as impossible or exotic as a trip to the Moon. And, as with going to the Moon, we had many obstacles to overcome before we could make the journey. Our mentally induced terror was perhaps the least of these obstacles.
Without technology, people don’t do very well breathing underwater, but even with the crudest devices, we have always striven to overcome this physical barrier. An Assyrian relief from 900 B.C. shows a man swimming underwater, breathing from a hand-carried bladder, not unlike those used for wine. In the fourth century B.C., Aristotle described a simple diving bell that allowed divers to descend to the bottom, swim about, come back to the bell for more air, and continue their underwater activities. All manner of diving dress and helmets were used through the ages, with varying degrees of success. Salvaging sunken ships for their cargo, cannons, or treasure provided economic incentive. If simple curiosity did not help us overcome our initial fears and superstition of the water, greed did.
The first truly successful diving apparatus was invented by the Englishman John Lethbridge in 1715. He described his device in an article published in Gentleman’s Magazine in 1749. It consisted of a tubular structure made of wood and resembling an elongated wine barrel, sealed with resin, and reinforced with iron rings. The tube was laid flat, and a man would climb into it through the head end, and lie facedown. In this position he could peer through a tiny porthole. He would put his arms through two short sleeves made of leather that protruded from the body of the cask, so he could perform actions with his arms free. The head end would then be sealed, and the tube lowered so the diver remained flat, facedown. Air was not supplied. Once the diver was sealed in, he breathed only the air he had. Down he went. He would work on the sea bottom with his leather-enclosed arms and signal the surface by means of a rope when he wanted to be hauled to the surface for fresh air. On the surface, two plugs would be removed; a bellows would be inserted into one hole and fresh air pumped in, and the stale air evacuated through the second hole. As might be imagined, dive times under such circumstances were limited: Lethbridge declared that he went to depths of 60 feet for up to thirty-four minutes with this contraption. He also reported that he went to depths of 70 feet and, with British understatement, that this was achieved with much greater difficulty. At the time the article was published, Lethbridge himself had been diving for three years with his device.
The limited time that Lethbridge could spend on the bottom was a blessing in disguise—had he stayed longer he would have encountered the difficulties of decompression. Although it seemed unlikely, that blessing was revealed as a by-product of new inventions that made possible a flourishing industry of the industrial revolution: bridge and tunnel building.
In 1841, the French mining engineer M. Triger developed the first working caisson, a watertight chamber that enabled men to work in compressed-air environments underwater to build bridge foundations, tunnels, and other underwater structures. A hollow steel tube was floated to the area by barges and placed upright so that it rested on the bottom, but its top protruded from the water’s surface. A ladder inside the tube allowed workers, known as sandhogs, to commute back and forth between the surface and the caisson on the riverbed, where they worked. The caisson didn’t have a “floor,” but air, pumped from the surface by a compressor, exerted a greater pressure on the water than the water on the air and prevented flooding. Compressor failure would mean that water entered as the sandhogs breathed the air that held back the seawater. The sandhogs dug into the river’s bottom, removing loose sediment and passing it up to the surface to be disposed of. As the caisson sank deeper, extensions were added at the top. When the sandhogs could no longer dig loose sediment but had hit a solid stratum, the caisson was filled with concrete to form the base of a bridge tower.
After the initial success of this radical new work method, the caisson was widely employed, for example on the Brooklyn Bridge construction. But it was noted that strange things happened to the sandhogs. As they ascended after their work shift, many experienced pain, paralysis, and even death. Thousands of workers were afflicted with the malady they called caisson disease. Coal miners had also been known to have these symptoms. Even though they weren’t surrounded by water, coal miners and sandhogs worked in a high-air-pressure environment. Now, not only coal miners but also sandhogs were ending up bent, crippled, and dead. Caisson and mine work was of course extremely hazardous, but at the time, caisson disease was viewed as just another consequence of industrialized work, and was deemed inevitable. As fast as workers were disabled or killed, others filled their place in this relatively high-paying type of unskilled manual labor. For his brilliant invention of the caisson, Triger received the prestigious engineering award the Prix de Méchanique, in 1852.
Prior to the time that Triger’s caissons were gaining widespread popularity with construction companies, commercial diving entered a new era. In England, Charles Deane had patented a breathing device conceived to aid in firefighting. In 1823, he and his brother, John, modified the device and turned it into a diving suit supplied with compressed air by a surface bellows. This suit allowed divers more time on the bottom than the Lethbridge contraption, yet the Deane brothers realized the need for an even stronger suit with a better gas supply: Lucrative ship salvage contracts awaited them if they could reach deeper depths for longer bottom times. They drew up specifications for a copper helmet that could be supplied with compressed air from a surface-based piston-type air pump. The German entrepreneur Augustus Siebe started manufacturing the Deanes’ hard hat in England in 1827.
Dive times were greatly extended with the surface-supplied hard hat—but not without a price. When divers surfaced, they sometimes noticed lack of function in their arms or legs or pain in their joints. In extreme cases, they were in such pain that they cried out and curled into a fetal position. It was this symptom that led divers to call the malady “the bends” and say that the bent diver had “taken a hit.” It debilitated divers, crippled them, and even killed them. No one knew why. Perhaps the sea was a forbidden realm after all. Some cultures believed that the divers’ malady was caused by a spell put on them when they intruded upon mermaids, or by some other evil. Some divers who suffered the bends and thereafter on land were cripples who had difficulty moving their legs and hands were amazed that when they went underwater they could function like young men again. They thought the sea had cast a spell and would not let them go.
Yet diving deaths did not always come in the form of the bends. The earliest air compressors were hand-powered and required one or two men to crank a large wheel to keep air supplied to the diver in his waterproof canvas suit. If the men got tired of pumping, or the compressor failed for some other reason while the diver was deep, the water pressure literally squeezed the diver’s body. In extreme cases, if he was deep enough, the diver’s body would be squeezed up into his helmet. When the diver was hauled to the surface, topside personnel found a bloody blob of mush in the helmet, and sometimes in the air hose. They were horrified. In an attempt to prevent suit squeeze, and to contain the overcompressed remains, a one-way valve was invented and inserted into the air hose, just above the helmet. With the new valve installed, a compressor failure now meant that the diver would not be squeezed to death but would suffocate as he consumed the oxygen within the air trapped in his suit.
Diving was expanding rapidly, and in 1870 the Siebe-Gor
man Company was founded in England to manufacture diving suits and helmets to meet the needs of the growing industry. Siebe’s company is still in business and the “hard-hat” suits it makes are still in use; the distinctive Siebe-Gorman helmet is a universally recognized diver symbol.
As more men applied highly developed mechanical skills in the lucrative field of commercial diving, more divers got bent. The British Royal Navy also noted a high incidence of the bends among its divers. Some solution to preserve the investment in diver training and experience was required. In 1906 the British Admiralty hired the services of a Scottish physiologist, John Scott Haldane, to solve the bends mystery. Haldane first reviewed data gathered on sandhogs who built the Brooklyn Bridge, which was constructed from 1869 to 1883. He also conducted experiments in a recompression chamber.
Haldane knew that sandhogs, coal miners, and divers all breathed compressed air, which has the same composition as air on land at sea level. Nitrogen in the air would enter the lungs during inhalation and then be carried into the bloodstream and from there would be forced into the tissues. This nitrogen was more than the body was used to holding. As early as 1878, the French scientist Paul Bert determined that the bends was caused by excess nitrogen released from tissues and blood as pressure on the body was eased. Bert discovered that the nitrogen formed bubbles in the bloodstream that gathered around the joints, cut off the flow of blood, and pressed on nerve endings. On the basis of Bert’s findings and other data at his disposal, Haldane experimented on goats; he put them under pressure, and simulated various depths for different lengths of time. Haldane observed that when a goat has pressure-induced joint pain, it kneels, the goat’s equivalent of a bent diver’s urge toward the fetal position.
The Last Dive Page 8
