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Tom Mount (1939-2022) Brought Considerable Depth and Experience to Technical Diving

Though most tech divers have heard of Tom Mount and the International Association of Nitrox and Technical Divers (IANTD), it’s likely only a few insiders know his back story and about the considerable depth and experience he brought to what would become known as technical diving. Here author and Asian tech pioneer, Simon Pridmore takes us on a deep dive into Mount’s many achievements. May he rest in peace.



By Simon Pridmore. Header image, “The old warhorse —Tom Mount post-dive 1993 Ginnie Springs. Photo by Kevin Denlay

In January, when the news emerged of Tom Mount’s death, Facebook lit up with hundreds of messages from right across the acquaintance spectrum. Some were from close friends who had known Tom for many years; others were from people he had only met briefly or quite recently. Some comments even began with the words, “Although I never got to meet Tom…” and then went on to express their sadness at his passing.

Tom Mount
Courtesy aquaCORPS archives

Condolences poured in from all over the world, not only from Florida and elsewhere in the USA, but also from Central America, the UK, Europe, Southeast Asia, China, Australia, New Zealand, Micronesia, pretty much everywhere people scuba dive. Many were from countries Tom never visited, written in languages he didn’t speak.

He was 82 when he died. If in 1989, you told the then 50-year-old Tom Mount that his death would send a minor tremor right around the diving world, he would have been astonished. Up to that point, he had achieved a great deal, but he was little known outside America. Within a few years, his fame would be global.

How did this happen? 

As is often the case, to understand why the path winds the way it does, you have to go back and follow it from the start.


Tom was born Warren Thomas Mount in 1939. He learned to box when he was nine years old and thus began a lifelong passion for martial arts, which would both keep him fit into his older years and provide much of the philosophy behind his approach to scuba diving.

The US Navy taught him to dive. He joined up in 1957 and became a Navy diver. He was also attached for a time to the Army Corps of Engineers and was primary author of the Army Corps of Engineers (Diving) Course Syllabus.

Mount getting ready to splash.
Mount getting ready to splash. Photo by Bret Gilliam


The Navy used both open circuit and closed circuit apparatus. Navy divers were introduced to the aqualung by its co-creator Emile Gagnan in early 1949 and, during Tom’s time, the rebreather units they deployed included the Draeger LT Lund II and the Emerson – Lambertsen UBA.

In the 1990s and beyond, Tom would subsequently become a passionate advocate for the use of rebreathers in sport diving. Inventors and manufacturers would beat a path to his door, seeking his advice. Dive Rite’s Lamar Hires was one of the beneficiaries. 

“We visited him in Miami and Jared and I went out on his boat. Tom and I took two units down to about 18m/60 f and tested them. I was new to rebreathers and needed his guidance on the design. He was very impressed with it but, more importantly, I got a one-on-one lesson about loop volume and trim. I remember watching Tom pull off weight because he was heavy and I proceeded to do the same thing. The discussions that followed helped shape the product.”

  • Buddy Dive Bonaire

Mixed Gas 

After leaving the Navy, Tom went to work as diving officer for Lockheed at Cape Kennedy (Canaveral), the base for NASA’s space program. 

In 1967, he took up a position as director of the Scientific Diving Program (SDP) at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science (RSMAS). The school’s website recounts how, under Tom’s direction:

“The SDP introduced mixed gas diving to RSMAS scientists.”

ANDI and IANTD agreeing on blending standards at the Tek.93 Conference.
ANDI and IANTD agreeing on blending standards at the Tek.93 Conference. Photo courtesy of aquaCORPS archives.

He ran the program from 1968 to 1976, when he left to spend two years with the YMCA as its national scuba programme training director. 

During this time, however, Tom often had matters other than work on his mind.

Going Underground

Just before leaving the Navy, he discovered cave diving. His first introduction was at Zuber Sink, northwest of Ocala, Florida, later to be acquired by Hal Watts and renamed as Hal’s Forty Fathom Grotto. Watts and Tom first met around this time and were to stay firm friends to the end. 

Tom referred to these early days in a 1995 aquaCORPS magazine interview

“I started deep diving when I got out of the Navy in 1962 and I thought I was a real pioneer. I was shocked to find that people were (already) getting into the Andrea Doria and working at 250, 260 feet in caves.”

By 1963, both Watts and Tom were training cave divers and doing deep cave dives. Tom teamed up with Frank Martz to bottom out Zuber Sink at 240ft (hence “Forty Fathom”) and explore the hitherto unvisited depths of Lost Sink, later to become better known as Eagle’s Nest. In 1965, Tom and Martz set the world record for the deepest scuba dive on air with a descent to 110 m/360 ft, a record that stood until Watts and A.J. Muns dived to 120 m/390 ft two years later. 

They were at the pinnacle of their sport. In 1966, Sheck Exley, a man who was later to become one of the deep cave diving elite himself, did his first cave dive. Writing in 1984 and harking back to his very early days, Exley wrote:

“Now, for better or for worse, my life was set. Sports heroes…were now replaced by Mount, Watts, Harper on the list of people I most admired. Hal Watts was the best deep cave diver, Tom Mount had the most cave dives and was the best published and John Harper was simply the best, period.”

Tech pioneers L2R: Tom Mount , Bret Gilliam , Rob Palmer  and Richard Bull in Florida 1992.
Tech pioneers L2R: Tom Mount , Bret Gilliam , Rob Palmer and Richard Bull in Florida 1992. Photo courtesy of Bret Gilliam


In the late 1960s, Lithuanian Dr. George Benjamin became fascinated by the Blue Holes of Andros in the Bahamas and started diving in them. Long on enthusiasm but short on experience, as he began to explore deeper, Benjamin decided he needed help and invited Tom to come over from Florida to join him. Tom recruited other top Florida cave divers to form a team to push the cave system deeper and further. These included Martz, Tom’s then wife Zidi Goldstein, Ike Ikehara, Jim Lockwood, Sharee Pepper, and Dick Williams. 

In early 1971, Tom and Martz found a new tunnel with a restriction at 85 m/280 t. When the team returned in September of the same year, Martz was determined to try to go beyond the restriction. Benjamin was against the idea. He thought it was dangerous and conflicted with his plans. And he was paying the bills. Tom told Martz that the project was their priority, but Martz was insistent and eventually Tom persuaded Benjamin to allow the dive to go ahead. 

It was a story Tom would often tell.

“Frank died on a dive in Benjamin’s Cave in Andros Blue Hole 4 in the Bahamas on September 4, 1971. Frank and Jim Lockwood were going to explore a passage Frank had found on our last trip there. Zidi and I were to add line in the other passage. Prior to the dive I had a premonition one of us would have an accident. Normally I listen to my intuition, but on this dive I did not. Frank and I had argued earlier…so I thought my bad feeling was over our disagreement.

But I did continue to have the feeling as the dive started. About 25 minutes into the dive, I felt someone had died. It was not Zidi or me, and as we exited we saw Jim. Jim and Frank had got into a bad silt out and Jim felt Frank had passed him, so expected to see him on the way out. Zidi went up to decompress and Jim and I doubled back to try and find Frank. We pushed our air to the maximum and returned to decompress on oxygen.”

To this day, Martz’s body has not been found.

  • Buddy Dive Bonaire

The subsequent police investigation report quotes Tom as saying:

“Frank Martz was probably one of the best cave divers in the world…He was one of my best friends and one of the people you think it is impossible for them to die diving. He has done more to develop safe cave diving equipment than anyone and the cave diving world will miss him…” 

Tom always cited Martz’s death as a turning point. You can just feel his disbelief in his police statement. Subsequently, he and others came up with a variety of wild theories to explain how Frank had died. The possibility that he had just got something wrong was too hard to process.

Like other technical diving pioneers, the experience of losing a close friend to the sport would act as a driving force.

Tom Mount and Gary L. Taylor mixing on Elm Street. Photo courtesy of Gary L. Taylor.

In his book, Technical Diving from the Bottom Up, Kevin Gurr recalls:

“In the water, (Tom) was, and still is, a task master. I’d never heard anyone scream underwater before. You knew when you’d screwed up.”

That was Tom’s style. He could be absolutely terrifying; chewing you out in the darkness, half a mile into a cave, when you made a mistake. But behind the unintelligible bellowing was the message:

“My best friend, the best cave diver I knew, made a mistake and died in a cave. If it happened to him, it can happen to you and it will happen to you if you don’t focus constantly. Never again! Not on my watch!”


A few years earlier, together with Watts and others, Tom had already been involved in measures to improve safety standards in cave diving. The increasing interest and participation in the sport in the 1960s had led to a number of diver deaths, which in turn led to bad press and political pressure on land owners to close off access to the caves; even threats to ban cave diving altogether. 

Photo courtesy of Gary L. Taylor

In response, the USA’s first cave diving organization, The National Association of Cave Divers (NACD) was established to offer courses and certification in cavern and cave diving with the goal of improving safety. Those who assembled in Gainesville, Florida, on May 21, 1969, to sign the articles of incorporation were Tom Mount, Hal Watts, Dale Malloy, David Desautels, Lawrence Briel, Ronald Wahl, James Sweeney, and Gilbert Milner. 

Tom was NACD training director and, after Martz’s death, wrote The Cave Diving Manual (1972), one of the first US cave diver textbooks (the very first was Exley’s Dixie Cavern Kings Cave Diving Manual (1969). Subsequently, Tom was lead author on Safe Cave Diving (1973), to which Exley also contributed.

In terms of his speaking voice, Tom was far from a perfect communicator, especially if you were not a native English speaker, his drawl and soft speaking voice making it difficult to pick up what he was saying.

Fortunately, over the years, he wrote it all down. The cave manuals were followed by Practical Diving: A Complete Manual for Compressed Air Divers (1975), written with Ikehara and published by the University of Miami.

Many more books would follow.

Photo by Kevin Denlay.


Survival was a common theme in his teaching and writing. He would frequently tell the story of an air sharing exit when he and a fellow diver both ran out of air a long way before the end of the cave, yet kept pushing on, finning regularly, not panicking, knowing that it was the only way they could survive. Two mantras that his students would hear time and again were:

“Only you can breathe for you, only you can swim for you, only you can think for you” 

“Survival is making the choice to continue and not quitting regardless of the odds.”

One DEMA Show, Tom was receiving an award in front of a large crowd and, in the front row, he spotted Don Shirley, one of South Africa’s top cave divers. Calling him up on stage, Tom told the story of how Shirley had survived an eight-hour ascent from a deep cave while suffering from devastating, crippling decompression sickness. Pointing to Shirley, Tom announced:

“This is the guy who deserves an award. He is a true hero. He survived when it would have been easier not to.”


Mindfulness, a concept borrowed from his martial arts training and his PhD studies, was another standout feature of Tom’s training technique. In his description of the circumstances leading up to Martz’s death (above), he talks about premonition and intuition. Tom saw developing awareness of these phenomena, and listening to your feelings as important components of a survival mentality. The course materials he developed also included advice for divers of the value of pre-dive visualisation and post-dive reflection.

Nowadays, technical diver training has come to accommodate all these aspects, but when Tom first introduced them they were radical and innovative. Divers being divers, they generated a certain amount of cynicism and Tom was dubbed Obi-Wan Kenobi (although not within earshot). During a course, divers would dread the meditation session at the end of a long day of caves and classes. The urge to fall asleep was almost impossible to resist. Nobody wanted to be the first to shatter the peace with a loud snore!

Tom Mount pre-visualizing a dive at Ginnie Springs.
Tom Mount pre-visualizing a dive at Ginnie Springs. Photo courtesy of Kevin Denlay

Tom saw introducing mindfulness to extreme scuba divers as one of the most significant elements of his legacy. In his TekDive USA 2016 speaker biography he wrote:

“…our primary strengths lie in the ability to use intuition and our use of Chi. (I consider) three elements of Survival and Existence to be the key to life.”

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Turning Point

During the 1980s, Tom wrote travel guides, took underwater photographs, and submitted articles for dive magazines. Together with Patti Schaeffer, who was to become his wife and business partner for the next two decades, he even published A Guide to Underwater Modeling (1983).

Tom’s author biography in this book gives a good idea of the scope of what he was doing around this period. He was running International Diving and Marine Consulting out of his Miami Shores home and was Marketing VP at Teach Tour Dive. He was also heavily involved with National Oceanic and Atmospheric Administration (NOAA) – the maritime equivalent of National Air And Space Administration (NASA) – as an aquanaut, a saturation diver and a contributor to both the NOAA Diving Manual and the NOAA diving programs, for which he received an award.

His life was about to undergo a radical change. When NOAA Deputy Diving Coordinator Dick Rutkowski retired in 1985, he formed the International Association of Nitrox Divers (IAND) and began to teach sport divers how to blend and use nitrox, which, up to that time, had been used extensively by the scientific and military diving communities, but ignored by the sport diving world. Rutkowski also linked up with Ed Betts in New York to start American Nitrox Divers Incorporated (ANDI). 

IANTD advert in aquaCORPS Journal
IANTD advert in aquaCORPS Journal

Having written the first nitrox diver training manual and workbook in 1989, the following year, Rutkowski sold IAND to Tom, although he remained on the Board of Directors.

In the USA in the late 1980s, the activities of various groups of divers who were involved in diving beyond the conventional limits began to gain more prominence. The groups started to coalesce and exchange ideas. Nitrox was part of this conversation, along with deep wreck diving, cave diving, diving on helium-based gases, oxygen decompression, and using rebreathers. A wave was building. 

Michael Menduno’s aquaCORPS Journal was the first magazine to focus entirely on what was going on in “beyond-limits” scuba diving and was highly influential in bringing the tribes together. In the January 1991 issue of aquaCORPS, Menduno trialed the phrase “technical diving” as a catch-all term for these activities.

He wasn’t the only one to find this an apt description. Tom took note and added the word “Technical” to the name of his newly acquired training agency, so it became IANTD. 

Just as in the late 1960s, when there had been no training agency offering formal education and certification for people who wanted to dive in caves, similarly, when the 90s began, no organisation existed that offered the same for aspiring technical divers. As with cave diving, from a safety and liability point of view, there was an obvious need.

If you had wanted to design an individual to start such an organisation, you couldn’t have done much better than Tom Mount. If he hadn’t existed, someone would have had to invent him. He had a background in building diver training agencies and writing textbooks, he had been diving with rebreathers since the 1950s, deep diving since the 1960s, and working with mixed gas since the 1970s. He also had prestige and status among extreme scuba divers – in 1995, aquaCORPS dubbed him a “gray-beard” of cave diving. (Tom was 56! Already an ancient seer from Menduno’s comparatively youthful perspective.)

One of the first books on mixed gas scuba diving. Published in 1992

Not only could Tom ride this wave, he could get ahead of it and be one of the leaders of the new movement. He added new members to his Board of Directors who would fill in some of the gaps in his skillset and access. IANTD may have been a band in which he could play all the instruments, but he was not a natural lead singer.

The two people he chose fit the bill perfectly: The first, Bret Gilliam, was someone Tom had known since his Andros days. Gilliam was a serial successful entrepreneur with a wide network of contacts, a gift for marketing, and a deep diver who had just set a new world record for deep air diving. Gilliam thought:

“Tom was one of the most skilled divers I had ever met, and we had so much in common.”

In 1992, Gilliam would publish a book called Deep Diving through Ken Loyst at Watersport Publishing and he and Tom would team up to write Mixed Gas Diving for Loyst the following year. These were the first technical diving textbooks, and both became worldwide bestsellers.

The second recruit was Capt. Billy Deans, who had developed mixed gas diving procedures in Key West, Florida, and had been introducing deep wreck divers in the US Northeast to his systems. 

Gilliam and Deans were both charismatic figures with front-of-house personalities, big reputations, and connections to parts of the technical diving world beyond the Florida caves – just what Tom needed.

The  first three IANTD trained Open Water Diver Instructors - 14th May 1993 - with Instructor Trainer Tom Mount and two assistant instructor Rottweilers.
The first three IANTD trained Open Water Diver Instructors – 14th May 1993 – with Instructor Trainer Tom Mount and two assistant instructor Rottweilers. Photo by K. Denlay

His next task was to develop standards, procedures, and teaching materials for a mixed gas and planned decompression diving training program that could both stand on its own and bolt on to the existing sport diving education pyramid. Tom was in familiar territory. After all, he had already authored training programs for groups as varied as Navy and Army divers, scientists, cave divers and the YMCA. 

The entry point was the nitrox diver course, introducing divers to gases other than air. The next step was planned decompression dives; then dives using multiple gas mixes. With each subsequent level dives became deeper and longer. 

The top step on the pyramid was trimix diving; that is, diving with a helium-based bottom gas, a travel / first decompression gas and a final oxygen rich decompression gas. This course would certify sport divers to explore depths to 300ft. As Tom told Menduno in his 1995 aquaCORPS interview, it was not something they entered into lightly.

“We had a lot of concerns about trimix when we got started. In fact, Billy [Deans] and I, and a bunch of other people, talked about it for two years. “Do we really want to take the responsibility of certifying somebody as a trimix diver?” There was a lot of trimix teaching going on, but no one had actually said, “You are a certified trimix diver.”
Remember, there was no insurance for this stuff in those days; it didn’t exist. Eventually, we went ahead and developed training programs and standards.”

  • Buddy Dive Bonaire

One of Deans’ early trimix students in the precertification days was author, journalist, and pioneer deep wreck diver Cathie Cush. She remembers that she was one of a select few.

“Billy Deans said that only about 20 divers did his trimix program in 1991, and he had another 20 at a single program in New Jersey in spring of 1992. Of course we wanted to go deeper, stay longer, be safer… And we knew we were pushing it with deep air. We just had to figure out how to do mix in scuba tanks instead of with hoses.”

The technical training pyramid Tom designed became the template that every major sport diver training organisation would follow as they all eventually developed their own technical diving programs.

Tom Mount and author Simon Pridmore with trimix students in Thailand in 1997."
Tom Mount and author Simon Pridmore with trimix students in Thailand in 1997.”

Magic Beans

Although the word had been in the company name from the beginning, IAND / IANTD had not been very international in its early years. In 1991, that was all about to change.

Word spread beyond US shores that Tom and Co. had the magic beans, and people from all over the world climbed up the beanstalk to Florida. The English speakers came first; the Brits in the vanguard, followed by the Australians. As Kevin Gurr remembers, when he, Richard Bull and Rob Palmer arrived to learn the secrets of mixed gas diving:

“You were taught in Tom’s house and often ended up sleeping with one or two Rottweilers after a long day’s diving. The only text was Dick Rutkowski’s Nitrox Diver; everything else you learned by example… On land the lectures often took the form of open discussion because we were all learning.”

The Brits were planning to start their own pan-European technical diving agency, but in the end Gurr became the first overseas IANTD licensee. Others were to follow: today there are 23 international IANTD licensees covering the entire globe. In the field of scuba diving, this was a groundbreaking business model.

  • Buddy Dive Bonaire

It was also a pain in the neck. From running a small local company, Tom suddenly found himself at the head of a global empire, fighting fires on four continents, trying to maintain quality control among those who came and signed a contract that empowered them to rule their own faraway IANTD kingdom in his name. 

Some were worthy acolytes: others proved not to be as reliable as hoped. Selecting the right individuals was very difficult. After all, how can you assess a person’s character and potential on the basis of a relatively brief acquaintance and when you know nothing about them beyond what they have told you themselves? In those days, you couldn’t just Google someone. 

Tom decided to judge people by what he could see for himself – how they dived, how they dealt with the cave, and how they understood his ethos. You would not graduate and become part of the IANTD system until you had been “Mounted”, as some called it. Tom would organise huge international gatherings in Lake City, roping in trusted cave instructors, like Larry Green and John Orlowski, to help run the training. 

Mostly this technique was successful. Sometimes it wasn’t. Some of the folks who came and took away the magic beans had personal agendas and had to be disciplined, although this was often hard to do at a distance, even with online communications in a flattening world. The mountain is high and the king is far away, as the Chinese say.

The arrival of the Internet meant Tom didn’t have to fly off to other parts of the USA or foreign lands to respond to criticism, deliver rebukes or demand change; he could fly off the handle on an email or in a chat room instead. He never pulled a punch, and some of his exchanges were legendary in their fury. People who had only met polite, smiling, soft spoken Tom in his land-based life were surprised. Anyone who had ever been on the receiving end of Tom’s reaction when they did something wrong in a cave was not surprised at all. 

While Tom was teaching disciples, building a network, fighting online battles, wrestling technical diving into manageable shape, and making sure his training programs had legal footing, he had a solid team behind him in the office, led by Patti, son David, and Don Townsend.

By 1995, Menduno, writing in aquaCORPS, summed up the state of play thus:

“It wasn’t too long ago that technical diving was regarded as the lunatic fringe of sport diving… “You’re going to do what?”
Enter Tom Mount. In less that five years, the 56 year-old former U.S. Navy diver… and one of the graybeards of the NACD… has built the world’s largest technical diving agency, pulling together the lion’s share of the “big names’ in more than a dozen countries under the IANTD banner. Considering the egos involved – no small feat indeed.
Under Mount’s leadership, IANTD has created a structured series of technical diving courses and training standards, has nailed down an insurance program providing coverage at depth and spun off at least one other agency.” 

This “spun off” agency was Technical Diving International (TDI), established in 1994 by Bret Gilliam and Mitch Skaggs. It too would come to span the world. 

 Tom Mount and Michael Menduno at TEKDive USA 2018.
Graybeards are we? Tom Mount and Michael Menduno at TEKDive USA 2018. Photo courtesy of M. Menduno


Industry acceptance of technical diving—something Tom and others had fought hard for—was cemented in the late 1990s, when the mass-market training agencies expanded their range to include nitrox and technical diving, but this victory brought its own challenges. IANTD, TDI and ANDI no longer held a monopoly. Nevertheless, the IANTD empire continued to grow, especially overseas. In the beginning, of course, the USA had been the most successful office in terms of certification numbers. A few years later, it was Central Europe. Then it was Korea. The fulcrum of scuba diving was moving east and the licensee business model meant that IANTD was there already. Another consequence of the expansion was that Tom started travelling further afield to run courses in places such as Pattaya, Thailand and Bikini Atoll in the Marshall Islands.

Deans eventually hung up his fins, and US Navy Commander Joe Dituri came on board as a director. In 1998, Tom published the Technical Diving Encyclopaedia, which would become the seminal text for a new generation of advanced divers, just as Mixed Gas Diving had been for their predecessors.

In 2000, the Academy of Underwater Arts and Sciences honored Tom with a NOGI award for Sports Education. Movie director and fellow NOGI awardee James Cameron described getting a NOGI as “the underwater equivalent of winning an Oscar except a lot harder!” 

In 2005, after a hectic 15 years at the helm of IANTD, retirement seemed to be in the cards, as the company was sold, only for the deal to fall through in traumatic  fashion. Dituri, the international licensees and old friends kept the wagon rolling and Tom eventually returned to pick up the reins. It was not until 2015, when Luis Augusto Pedro came on board as COO, that Tom could move out of the front line and spend more time with wife Gexa. 

Nevertheless, he remained CEO and figurehead, he was still often spotted wading into the ocean with a new rebreather model on his back and he was still writing until well into his seventies.”The titles of the Tao of Survival Underwater (2008) and the Tao of Cave Diving Survival (2016) show how, over 50 years, the times might have changed, but the basic themes and messages remained the same.

By now, he could genuinely enjoy being a “gray-beard,” accepting further awards and speaking invitations and, as his Facebook page shows, attending events and meetings and befriending yet another crop of technical divers – the only difference being that this new generation demanded selfies.

Tom Mount RIP.

Photo courtesy of the aquaCORPS archives


Tom was never one to blow his own trumpet. He did not write an autobiography, rarely agreed to interviews and, when asked to supply an author or speaker biography, usually did no more than list his awards and accomplishments. This piece has been compiled from a host of sources, including personal memories, recollections of conversations with Tom over the years, input from some of Tom’s friends and colleagues, and details of Tom’s life and opinions gleaned from books and the few interviews he did give. 

Additional resources:

Facebook: Tom Mount

Wikipedia: Tom Mount

IANTD: Training with Tom Mount Classes (Wayback Machine 1997)

PSAI: Tom Mount and PSAI 

IANTD: The Early Evolution of Technical Diving – Overview

aquaCORPS: You’ve Come A Long Way Baby: Tom Mount Talks Tech by Michael Menduno (1995) Deep Diving: An Advanced Guide to Physiology, Procedures and Systems, by Bret Gilliam, Robert Von Maier, John Crea Mixed Gas Diving: The Ultimate Challenge for Technical Diving by Tom Mount, Bret Gilliam et al Technical Diving from the Bottom Up, by Kevin Gurr

Divernet: THE TECHNICAL DIVING REVOLUTION – PART 2 by Michael Menduno (2019)

Simon Pridmore was a pioneer of technical diving in Asia. Today, he is one of diving’s most prolific writers, with a five volume Scuba series, several guides for travelling divers, a biography and even a couple of divers’ cookbooks to his name. He is currently working on a new book called Technically Speaking, a collection of talks about technical diving, including the history of tech, what went before, how it came about and why things developed the way they did. Learn more about Simon and his books on his website or via his Scuba Conversational newsletter.

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Karen van den Oever Continues to Push the Depth at Bushmansgat: Her New Record—246m

Karen van den Oever recently broke her own world cave diving depth record by a little more than 10m/33 ft at Bushmansgat cave in South Africa. The S.African cave diver conducted the 8 hour 14 min high-altitude dive on open circuit scuba, breathing trimix 4/90 bottom mix, and suffered mild High Pressure Nervous Syndrome (HPNS). Here former world depth record holder, Nuno Gomes who was van den Oever’s cave instructor, offers the details of her record setting dive along with a short history of the women’s depth records.




By Nuno Gomes. Images courtesy of Karen van den Ever.

Karen van den Oever and her husband Francois Bain

Karen van den Oever, from Johannesburg, South Africa, has dived to a depth of 246.65 m/809 ft. This is equivalent to a dive to a depth of 296 m/971 ft when corrected for an altitude of 1550 m/5,085 ft above sea level. The dive was conducted on October 27, 2022, in Bushmansgat cave, South Africa, and is a new women’s world record cave dive. Karen bettered her own previous world record to a depth of 236.04m/770 ft  (283 m/924 ft correcting for altitude), also accomplished at Bushmansgat cave in 2021.

I actually felt really good after the dive, a little tired but overall, quite good. I felt much better after this dive than the previous one. I’m happy that the dive went well, just thinking about what comes next. I have no definite plans going forward, we are looking into diving some of the caves in Namibia and also exploring some of the caves not yet dived in Zambia but no concrete plans yet.”—Karen van den Oever

Karen and Theo van Eeden, with the signed tag.

Women have been making record deep dives for quite some time. Back in 1981, one of the first deep diving records was made by Sheck Exley’s wife, Mary Ellen Eckhoff (USA). She used a dive propulsion vehicle (DPV) to travel into Wakulla Springs cave, as well as staged tanks for decompression purposes. Mary Ellen dived on open circuit, together with Paul DeLoach and John Zumrick, and they reached a distance of 363 m/1192 ft and a depth of 80 m/260 ft, which was a major dive at the time.

In 1996, Dr. Ann Kristovich (USA), a friend of Jim Bowden, considerably extended the record, reaching a depth of 167 m/548 ft on open circuit at Zacaton cave, Mexico. Ann’s world record dive would remain in place for a long time.

It was not until the year 2000 that another woman, Claudia Serpierri (Italy), would beat the previous record, but this time in the sea (Mediterranean Sea). Claudia would reach a depth of 211 m/692 ft on open circuit, diving from a support ship. This dive remains the deepest sea dive by a woman to date.

Toward the end of 2001, Verna van Schaik (South Africa), was ready to challenge the women’s record. First, she did her deepest dive by reaching a depth of  186 m/610 ft  (223 m/732 ft correcting for altitude), on open circuit, at Bushmansgat cave in South Africa. This was not enough for her, and during her next expedition on October 25, 2004, Verna would go back to Bushmansgat cave to become the first South African woman to get her name in the Guinness Book of World Records by reaching a depth of  221 m/725 ft  (265 m/870 ft altitude corrected), on open circuit. Her deep support diver was the late Dave Shaw (Australia), on closed circuit, who died of respiratory insufficiency at a sub-250 m dive at Bushmansgat in 2005.

View of the surface pool of Boesmansgat cave.

Following Verna van Schaik’s dive at Bushmansgat cave, two women divers died trying to break her record, as follows: 

In May 2010, French diver Brigitte Lenoir, died in Dahab, Egypt during a dive in the Red Sea. The accident took place at 147 m/482 ft while ascending from a 200 m/656 ft, on closed circuit. Her body was recovered with an ROV. 

In September 2017, Bulgarian technical diving instructor trainer, Teodora Balabanova, died attempting a dive to 231 m/754 ft, on open circuit, while her husband, Mihail Balabanov, suffered from decompression sickness. 

Karen van den Oever is a science graduate from the University of Witwatersrand in Johannesburg, South Africa, where she currently resides. Like Verna van Schaik, who now resides in New Zealand, she is a CMAS diving instructor, and also a former member of the University of the Witwatersrand Underwater Club. 

Her original cave, trimix and blending training was with me. I also trained her husband Francois Bain. 

Unstoppable Karen van den Oever

Karen had previously dived to 201 m/660 ft (241 m/792 ft altitude corrected) on open circuit in Bushmansgat cave in South Africa’s Northern Cape province on February 27, 2020. That dive’s total dive time was 7 hours and 21 minutes. On March 26, 2021, Karen dove to 236.04 m/770 ft (283 m/924 ft), on open circuit, at Bushmansgat cave, using a bottom gas of trimix 6/85. The total dive time was 7 hours and 18 minutes. That dive is the current deep diving Guinness World Record (women).

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Karen’s new world record dive, done on October 27, 2022, was made to a depth of 246.65 m/809 ft (296 m/971 ft), in Bushmansgat cave. The dive was done on open circuit, using a bottom gas of trimix 4/90, and with a total dive time of 8 hours and 14 minutes. The dive would not have been possible without a large team of support divers. 

Karen’s dive computer. Actual depth from rope measurements by independent witnesses was 246.56m/809 ft.

Peter Reid was at 209 m/686 ft (251 m/823 ft); this was his personal deepest dive on closed circuit, and his total dive time was 6 hours and 20 minutes. Don Hauman did deep support at 110 m/361 ft (132 m/433 ft). Her husband Francois provided shallow support and surface support, together with the other team members.

Karen’s support team.

Karen’s Total Narcotic Depth (TND) was 48.06 m/158 ft; the Equivalent Narcotic Depth (END) considering nitrogen only was 9.49 m/31.14 ft, and her maximum Partial Pressure of Oxygen (PO2) was 1.03 Atm. Gradient factors: 40/75.

There were no serious incidents during the dive except that Karen suffered some mild High Pressure Nervous Syndrome (HPNS), which ultimately did not prevent her from going any deeper. Karen had some difficulties recovering the evidence tag from her maximum depth because of the tremors that she was experiencing as a result of the HPNS, but in the end she turned the dive mainly because she ran out of bottom time. 

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Nuno Gomes is a professional civil engineer, a CMAS technical diving instructor and a commercial diver. He was born in Lisbon, but his family relocated to South Africa during his youth. He now lives permanently in New York with his family. He has dived all over the world.

He used SCUBA (open circuit) to dive to a depth of 321.81 meters (1,056 feet), inclusive of rope stretch, in the Red Sea off the coast of Egypt near Dahab, in June 2005. The total dive time was 12 hours and 20 minutes. The descent took 14 minutes with two minutes spent at the bottom.

He also used SCUBA (open circuit) to dive to 282.6 meters (927 feet) in the Bushmansgat cave, in South Africa, in 1996. The cave is located at an altitude of 1,550 meters (5,086 feet) above sea level, which resulted in a decompression schedule for an equivalent sea level dive to a depth of 339 meters (1,112 feet) in order to prevent decompression sickness. The total dive time was 12 hours and 15 minutes with four minutes spent at the bottom of the cave.

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