Crucible, Part I: A Deep Dive Into the Early Days of Technical Diving

Ed. – In this two-part series, we present one chapter, called “Crucible”, from Simon Pridmore’s book, Technically Speaking: Talks on Technical Diving, Volume 1: Genesis and Exodus, which draws the bolts and picks the locks on the vaults in which are stored the memories of a time in the not-so-distant past, when the sport of scuba diving was on the cusp of change. It is a deep, deep dive into the early days of technical diving that explores how it all happened, why it all happened and who made it all happen.

These methods and technologies were born among individuals and groups of sport divers in the United States several decades ago. Not only did these pioneers use their own experiences, enterprise and creativity to work out how to make safer, more efficient and longer-range extreme sport dives, but they also borrowed know-how from the military and scientific diving communities and turned it to their needs. 

Technical diving was the metamorphosis of these people and their efforts into a coherent movement.

But was it really a movement? At times, during the first half of the 1990s, for insiders, it certainly felt like it, even one with quasi-religious and revolutionary undercurrents. After all, what is it that religions and revolutions share? 
• An origin story
• An opposing force
• Messiahs, apostles and disciples
• Martyrs, heroes and legends
• Sacred texts and propaganda
• Slogans and symbols

Technical diving had all of these. The only thing it lacked was the kind of inspired leader with a brilliant idea that religions and revolutions coalesce around. This may have been for the best. After all, the driving forces in the disparate diving tribes who took technical diving forward were not the sort of folk who typically look for someone to lead them. They were mostly explorers with ambitions to go somewhere, see something or do something extraordinary, and they needed the means to achieve their goals and ensure, as far as possible, that they got back home again afterwards. 

Getting back home again was an essential element of this philosophy. Otherwise, what would be the point? Consciously or otherwise, they were borrowing the sentiment expressed by US President John Kennedy in 1961, that the aim was not just “landing a man on the Moon”, but “returning him safely to the Earth”. Safety was the major concern in technical diving from the beginning, although the opposition within the mainstream sport diving community did not see it that way, and there were times in the early days when tragic bursts of accidents did not make it look that way either.

However, in retrospect, technical diving was neither revolution nor religion. It came more from chemistry and physics than philosophy or politics. It was a product of several ingredients coming together simultaneously in the crucible of the US extreme diving scene in the 1980s and onward.

Some of the ingredients were situational. The development of the Internet and the flattening world offered improved communications and coordination, and technological advances in blending and boosting gave sport divers easier and safer access to gases. Increased awareness, accessibility and popularity in turn led to the establishment of businesses providing more professional equipment and consistent training systems.

But the most important ingredients were human, and in the very beginning, it was the interaction of a handful of key individuals that provided the spark that flared into what we would come to know as technical diving. 

These people are the subjects of this chapter. One was a notable guru from the military, commercial and scientific diving worlds who lent his expertise, status and gravitas to ambitious sport divers lacking in all these much-needed areas. One was a true revolutionary. The others were explorers. 

All were pioneers, all had unconventional methods, and none could be easily confined or defined. 

It is curious that, by the end of the 1990s, when technical diving had become part of the mainstream, for a variety of reasons, none of the five was still part of the scene. One had been lost. Others had drifted away. They had changed the sport diving world but were no longer part of it. Those for whom change had been the goal dropped out. Their work was done. Those whose influence on the sport had been incidental to their other work just continued along different paths.

They all became celebrities, although none sought fame. The community they had helped create needed icons, and their achievements happened to be iconic. They were the patron saints for the new acolytes and provided a good part of the myth and legend on which the sport was founded. Their places in technical diving’s Asgardian Halls are assured.

The actual architects of technical diving would be the savvy entrepreneurs, inventors and engineers, charismatic prophets, tireless trainers, cosmopolitan travellers, gifted writers and natural marketers within the community who would keep the flame alight.

But without these five people and their combinations and interactions, there would have been no spark. 

Did it all begin with the rebreather guy? Or the cave diver? Or the decompression guru? Or the captain? Or did it really start when the tech geek started writing about it all? As you look back in time, you find that the lines connecting them go all over the place; they cross, they separate, they reunite, and then they spin off in different directions. I am tempted to pursue this obvious cave-diving metaphor further, but instead, I will just tie it off here and leave you to attach more line as you wish.

Sheck Exley: Live Oak, Florida

Sheck Exley was part of the 1960s generation of US cave divers, and many considered him the greatest of them all. In the mid-1980s, though, Exley was not so sure. He had a problem, and it was becoming increasingly clear that he was going to have to solve it. His problem was helium. He did not like it, and he did not trust it. Diving with helium got you bent or got you killed. But if he did not start using it, he was going to get left behind.

In 1970, Hal Watts, one of the country’s earliest deep cave explorers and someone Exley looked up to, had suffered serious decompression sickness following a heliox dive in a sinkhole. Then, in 1975, Exley’s best friend Lewis Holtzendorff was the first to use mixed gas on a cave dive and died in the attempt, although it was not the helium that killed him. It was the pure oxygen he was breathing too deep during his decompression stops that caused him to convulse and drown. Nevertheless, as far as Exley was concerned, this was a further sign that helium was to be avoided. He would stick to diving with air. He liked air, he trusted the air decompression tables, and he knew he had a good tolerance for narcosis.

In 1980, Exley held the record for the deepest cave dive on scuba, at 104m (340ft). Then, cave diver Dale Sweet broke the record on a heliox dive to 110m (360ft). Exley took notice. Six months later, he successfully performed the same dive to the same depth using air. Who needed helium?

However, the following year, German cave diver Jochen Hasenmayer descended to a depth of 145m (476ft) in the Vaucluse cave in France on heliox and completed a successful ascent. Then, in 1983, Hasenmayer extended his record to 200m (656ft). 

Back in the United States, Exley was breaking distance world records in cave diving for fun, but in terms of depth, he was falling behind, and it was his aversion to using helium that was holding him back.

Exley knew Hasenmayer and had dived with him. Hasenmayer was no fool, and this gave Exley confidence. He obtained some commercial diving heliox tables that bottomed out at 122m (400ft) and did a couple of workout dives in Florida. These went well. Then he went off to Mexico with the aim of going deeper. He was a mathematics teacher by profession, and, confident of his math skills, he extrapolated the commercial tables to greater depths. 

In early 1987, he used trimix to dive to 158m (520ft) in Nacimiento del Río Mante in the Sierra de Cucharas mountains, Mexico, and two months later, he pushed the same cave to 201m (660ft). He had caught up with Hasenmayer. But, in Exley’s own words, at the end of these dives, he was “wasted”. They took everything out of him. He knew he had extrapolated the commercial tables as far as he could. He had reached the outer limits of their validity, and he could no longer trust them. If he was going to go deeper, he would need to find another way. 

Earlier, at around the same time that he was preparing for the Mante dives, Exley was invited by Dr Bill Stone to join his Wakulla Springs project.

Bill Stone, Exley: Huautla Plateau, Mexico

Like Exley, nobody ever accused Bill Stone of doing things the normal way. He was a caver first, then an expedition caver. He started in Pittsburgh, then moved on to West Virginia, before heading south to Austin, Texas, primarily because it was close to some great caves, not only in the United States but in Mexico too. 

It was in Texas that he learned to dive in caves, but it was a visiting British cave diver who taught him, so he acquired UK-style, side-mount sump diving techniques. At the time, this was certainly not the way Americans dived in caves. But Stone was never part of any community. He was always an outsider.

In 1979, he jammed a regulator into his mouth and dropped into the San Agustín sump, a narrow, twisted, flooded tunnel over a kilometre below the surface of the Huautla Plateau, a limestone mountain in Southern Mexico with an enormous network of caves beneath. 

To save weight and bulk during the long, multi-day descent to the sump, he had brought neither fins, BCD nor weights and had only two small, side-mounted pony cylinders to breathe from. The buoyancy of his wetsuit meant his only possible strategy was to crawl upside down along the tunnel ceiling, in the style of vampires and other demons in horror movies. He scrabbled along, finding no end to the sump. Meanwhile, he was going deeper and consuming 100psi from the pony cylinder with each breath. He would have to go back. But before he did so, he turned and looked down. 

“The tunnel’s floor had simply disappeared. In its place stretched a crystal-clear sea of unfathomable depth.”

Following the cave through this sump to see what lay beyond became an obsession that would haunt Stone for the next 15 years. He anticipated that he would need to go much deeper to get through it, and this time, he sought advice and expert tuition closer to home and contacted Sheck Exley. Stone would later credit Exley not only for giving him the necessary skills to pursue his quest but also for saving his life when he found himself disabled by narcosis on an air dive to 70m (230ft) inside Florida’s “Eagles Nest” cave.

Next, Stone founded the United States Deep Caving Team, a rotating, non-profit group of expert volunteer cavers. Further expeditions to Huautla in 1981 and 1984 failed to realise his ambition. The 1984 trip, which tried to reach the far side of the San Agustín sump from another cave, which Stone thought might connect, involved diving through so many sumps just to get to virgin territory—and diving to depths as great as 54m (180ft)—that they no longer had enough air to push on further and be able to return. 

They had reached the limits of the available technology. The logistics and time limits imposed by open-circuit scuba would not permit further progress. Stone still believed the Huautla cave continued beyond the sump. He just had to find another means to get there. 

One of the members of the Deep Caving Team was Dr John Zumrick, whose full-time job was Chief Medical Officer at the Navy Experimental Diving Unit (NEDU). After the 1984 trip, he suggested Stone look at the closed-circuit scuba diving systems that the US Navy was using.

Stone quickly identified this as the technology he needed but concluded that the Navy units were too fragile to be transported along several kilometres of tortuous cave passage. He was to spend the next three years designing and then building the first version of his Cis-Lunar rebreather. 

When it eventually appeared, it weighed 93kg (205lbs), and it was called FRED (Failsafe Rebreather for Exploration Diving). FRED was a big boy—someone once said it was like diving with a Volkswagen on your back—but, at this point, Stone was not concerned with size. Once he knew the technology worked, he could concentrate on making it smaller. As it was to be used for cave exploration, in addition to being indestructible, it had to be, in Stone’s engineering parlance, “fault-tolerant from the ground up”. Redundancy was also essential. In fact, the unit was two separate rebreather systems in one very rugged box.

The Cis-Lunar Mark I was supposed to be finished in 1986, in time for Stone to take it to Andros in the Bahamas for an expedition being run by Rob Palmer’s International Blue Holes Project. Stone had promised Palmer a rebreather, but as the deadline approached, it was still not ready. However, Palmer still wanted to take a closed-circuit unit with him, and by chance, he found an alternative option in the United Kingdom.

Stuart Clough and his company, Carmellan Research, had a rebreather they were developing, and he agreed to bring it over to Andros. But Clough could only give the project 10 days of his time, so after he and his team had departed, Palmer and Stone were still left with a lot of Blue Hole cave diving to do. 

They spent the following month diving with heliox on open circuit, collecting stalagmites, accumulating data and gaining mixed gas diving experience that was to be extremely valuable for Stone in Wakulla Springs the following year. Zumrick again was a great help, giving Stone advice on decompression schedules for helium-based mixtures based on NEDU experiments.

An even more valuable consequence of the trip was the connection Stone made with Dr Bill Hamilton, a decompression table specialist who had been working with Clough and had come out to Andros as part of the Carmellan team. 

Stone and Hamilton were fellow Texans, but beyond that, they found in each other a kindred spirit. They were both unconventional explorers, each in his own field, with the desire to look for solutions that others could not see and the ability to find them.

Dr Bill Hamilton: Tarrytown, New York

US Air Force veteran Dr Bill Hamilton earned his doctorate degree in physiology and biophysics at the University of Minnesota. In 1964, he began work as a scientist and director of Ocean Systems, an environmental physiology and diving research lab in Tarrytown, New York. He and his staff conducted extensive research on the effects of gases both under increased pressure and in hypobaric environments. This work led to the development of decompression modelling tools and operational procedures for divers, astronauts, hyperbaric chambers, and tunnel and caisson workers.

In 1976, Hamilton set up his own physiology consulting firm, Hamilton Research, Ltd. He worked extensively with oil companies, the military and others to develop procedures and techniques that could mitigate the effects of High-Pressure Neurological Syndrome (HPNS). 

He and his team also developed the Diving Computational Analysis Program (DCAP), a computer program that could create decompression procedures and schedules for a wide variety of exposures to pressure, including submarine escape, space travel, deep commercial diving, and caisson and tunnel work. 

This program revolutionised the way decompression analysis was done, and Hamilton Research began working with navies and research centres around the world. From the mid-1980s onwards, an irresistible attraction to the edge of the operational envelope led Hamilton to extreme sport divers and them to him.

Historically, only commercial and military divers had had access to mixed gas for diving operations. But now, cave divers and wreck divers wanted to go deeper and farther than air would allow them to go safely. So, Hamilton stepped out of his traditional role and entered a new diving world, populated by an entirely different type of individual.

Exley, Stone, Hamilton: Wakulla Springs, Florida

Back in 1986, Stone had obtained permission to dive in Wakulla Springs, a deep cave network which is part of the Floridian aquifer. His original priority was to test his new rebreather there and conduct some exploration on the side, but the state authorities would only approve the project if exploration was clearly stated to be the priority. 

Stone agreed and amended his application. In 1987, he commissioned Hamilton to develop a custom set of mixed gas decompression tables for extreme cave dives to 100m (328ft) on open-circuit scuba with managed oxygen exposures and minimal nitrogen narcosis. The divers would also be using long-range DPVs and a variable depth habitat for decompression. 

Note that this was four years before anyone even heard the term “technical diving”. Almost everywhere else, sport divers, including ultra-deep wreck divers, were still using air for everything and would continue to do so for several years yet.

Hamilton produced what was then a radical solution but is now a well-established procedure. He drew up tables that would have divers descending on heliox but switching on their ascent to various nitrox mixtures, then air in the habitat and finally pure oxygen. 

Exley was the first name on Stone’s list for the exploration team, which went on to explore over 3.3 kilometres of Wakulla Cave passage at depths to 90m (300ft). It was intensive, high-risk, long-range diving. The project was a huge success, and there were no cases of decompression sickness. 

Stone’s main goal for the tests on his new rebreather was to find out what kind of dive time he could get on it. With the help of teammates poking him every time it looked like he was falling asleep, he managed a 24-hour dive, breaking several records in the process.

Exley, Hamilton: Nacimiento del Río Mante, Mexico

Exley was impressed with what the Wakulla project had achieved. In 1988, he called Hamilton, told him what he had been doing at the Mante cave and asked for his help to go deeper.

On 28 March 1989, using tables devised by Hamilton and modified by himself, Exley completed a successful dive to 264m (867ft). His run time was 13 hours, 52 minutes. His bottom mix was trimix 7/69, and he used ten different gas mixtures during his ascent, two other trimixes, five nitrox mixes, air and 100% oxygen.

Hamilton received criticism in some quarters for working with divers outside “professional” circles. He was unperturbed. His conscience was clear. He would always begin by trying to talk divers out of their riskier projects (like Exley’s) but would do his best to help them if he assessed that, if he said no, they would do the dives anyway and possibly get hurt. 

Eventually, word of what Hamilton could do reached beyond the cave diving community. And that story will be told in the next issue. ■

^{Source for captions: Wikipedia}