Interview with Bret Gilliam: Trailblazer & Founder of TDI

If you love scuba diving, deep dark waters, decompression procedures and mixed gas theory, you must have heard the name many times: Bret Gilliam, a revolutionary trailblazer in the dive world. Over the past few decades, he has changed the way scuba diving is practiced.

Bret Gilliam, AUAS Diving Hall of Fame inductee 2012
Bret Gilliam being inducted into the AUAS Diving Hall of Fame in 2012

Contributed by

Bret Gilliam is a kind of living anecdote, a man with a thousand dive stories. Recently, I had the chance to sit and talk with him and hear some of his tales. We discussed hyperbaric medicine, diving records, the scuba industry and the future of closed circuit rebreathers (CCR) as well as open circuit.

Bret Gilliam aboard Calypso, filming with Cousteau
Bret Gilliam aboard Calypso, filming with Cousteau

Nothing appears as it really is. Gilliam is a kaleidoscope; getting inside his point of view requires time. So, take a deep breath and plunge into the mystic world that is Gilliam’s life, in which submarines, sea vessels, humpback whales and ocean exploration merge into one.


With a professional career that now spans over five decades, Gilliam has been involved in the dive industry since the early ’70s. Since he began diving in 1959, he has logged over 19,000 dives around the world. In addition to founding dive training agencies such as TDI, SDI and ERDI and dive magazines such as Scuba Times, Deep Tech and Fathoms, Gilliam’s background includes scientific expeditions, military/commercial projects, operation of hyperbaric dive treatment facilities, liveaboards and cruise ships, dive store and resort operations, equipment manufacturing (UWATEC), and filming projects for feature films, documentaries and television. He is widely recognized as one of the dive world’s most successful entrepreneurs.

Rob Palmer, Hans and Lotte Hass, Bret Gilliam receiving TDI Rebreather certifications 1997
True dive pioneers: Rob Palmer, Hans and Lotte Hass, and Bret Gilliam receiving TDI Rebreather certifications in 1997


His papers have been published by the International Society of Aquatic Medicine (ISAM), Divers Alert Network (DAN), Undersea and Hyperbaric Medical Society (UHMS), National Oceanic and Atmospheric Administration (NOAA), and South Pacific Underwater Medicine Society (SPUMS). He was also a contributing author and editor on the topic of “Diving Emergency Medicine” in the reference textbook, Prehospital Trauma Life Support, published by Mosby Lifeline, used by physicians, nurses, DMTs, EMTs and paramedics.

Bret Gilliam, National Geographic, Virgin Islands, 1977
Bret Gilliam filming for
National Geographic in
the Virgin Islands in 1977

Gilliam’s awards include NAUI’s Outstanding Contribution to Diving Award (twice) and Beneath the Sea’s Diver of the Year, as well as international recognition for his film work and photography. He is listed in the Who’s Who in Scuba Diving, published by Best Publishing, and was inducted into the internationally prestigious Explorers Club as a “Fellow National” in 1993. Gilliam has twice held the world record for deep diving on scuba and has been a leader in the growing field of technical diving, electronic dive computers, rebreathers and other technological advances. He was inducted into the Diving Hall of Fame by the Academy of Underwater Arts and Sciences (AUAS) in 2012 as a recipient of the NOGI Award. Currently, he serves as a consultant to businesses in the dive industry as well as a litigation strategist and diving/maritime expert witness.

AMA: Pick three words that describe you as a man, diver and professional. Please explain why you have chosen each.

Bret Gilliam with his father Gill, Bahamas, 1959
Bret Gilliam started diving at
age 8, seen here with his
father Gill, diving the
Bahamas in 1959

BG: As a man: “Caring;” as a diver: “Enthusiastic;” and as a professional: “Committed.” My whole life has been built around trying to be a good person who loves diving and is passionately dedicated to customer service, high-quality products, and good safety protocols. That’s the formula for success.

AMA: What was the dive that changed your way of seeing scuba diving? I mean, a dive that was like an epiphany, a dive that changed your point of view on technical matters...

BG: I began diving at age eight in 1959 in Key West, Florida. My father had introduced me to snorkeling and we watched the first television episodes of Sea Hunt that year. That show inspired me to take up diving, and my father allowed me to sign up for some of the first dive training offered in that era. I started my first business in 1961 at age ten, trapping fish to sell to the Key West Aquarium and to several others. I was making good money with my fish sales, and my little company was successful. That launched my initial involvement in diving, and I was hooked.

Bret Gilliam with USCG crew, Caribbean, 1977
Bret Gilliam working with USCG crew, for rescue training for aircraft/vessel sinkings
in the Caribbean, 1977

AMA: Can you describe the golden era of scuba diving, which you lived through? Was it a heritage?

BG: The dive industry was constantly evolving, and some incredible growth began in the early ‘70s. Professional dive facilities were created, as well as modern dive vessels, expanded certification training, astounding advances in equipment design, exotic dive travel… industry growth was superb. We began to see the decline in the late '90s as younger participants were not as attracted to diving as a sport. Since about 2003, we have seen the dive industry decline.

The leadership in the industry has also suffered, and with the current state of financial decline and the effects of the pandemic, I do not have a good feeling about the future. I sold the last of my dive companies in 2005, and it was the best decision I made. I am still involved in high-end book publishing and legal consulting. Many of us from the era developed very sophisticated and efficient business models in all segments, but many lacked the entrepreneurial skills and vision to achieve long-term success. When I sold the last of my companies, the aggregate value was about US$80 million. That’s almost beyond belief today.

Capt Bret Gilliam aboard Ocean Quest flagship Ocean Spirit, 1989
Capt Bret Gilliam aboard Ocean Spirit, the flagship of Ocean Quest International in 1989


AMA: As a captain, you have been merged with the sea, from the surface to its deepest points. What does the ocean or the sea represent for you?

Petersen, Tyson, Albbright, Gilliam, Coston excavating Santa Monica wreck, St John, 1972, with proton magnetometer
Dr Mendel Petersen (Smithsonian
Institution), George Tyson, Dr Alan
Albright, Bret Gilliam and Dave
Coston, excavating
the Santa Monica
wreck off St John in 1972, with their early proton magnetometer

BG: From my earliest experiences in life as a kid, the ocean has drawn me in. I learned to swim before I could walk and became an experienced snorkeler as a four-year-old. My father let me take scuba lessons at age eight in 1959. It changed my whole life. The ocean is my natural environment and my home. We face challenges with climate change, pollution, destruction of corals and marine life, etc. I hope the world can wake up to the grim reality that we face and take the necessary steps to save the oceans.

AMA: If you look to the past, can you describe the main steps in your scuba diving career and research?

BG: For 12 years, I was a sport diver doing all sorts of underwater jobs… cleaning vessel bottoms, taking out divers and snorkelers, fish collecting for the aquariums, photography, etc. I started my professional diving career in January 1971, working with the US Navy on their deep-diving projects in the Virgin Islands and handling the operation of the recompression chamber. After the Navy project, I moved into commercial diving and later became the manager of the company. I was lucky enough to work with some of the best professionals in dive research, including early work on decompression algorithms, physiology, dive treatments, saturation habitats, deep submersibles, and a seemingly endless list of other projects. For the last 50 years, my career path has been professional diving and vessel operations worldwide.

AMA: Who was the most influential person you have met in scuba diving?

Gilliam, Bonin, Walker at first VI Divers Ltd, 1974
Bret Gilliam, Dick Bonin
(founder of Scubapro) and
Bill Walker outside the first
location for V.I. Divers Ltd
in 1974


BG: Dick Bonin was an ex-Navy diver and then went on to found Scubapro. His insight, knowledge, expertise and wonderful personality bonded us. His mentorship was invaluable. We both made a fortune in diving. We were friends and colleagues for nearly five decades—a true pioneer, and I was so honored to know him.

AMA: You contributed to the history of diving with other great people of the recent past. Can you give us an account of the divers who were closest to you as your diving "family"?

BG: I spent 50 years in professional diving and was lucky to have some excellent colleagues to work with. One of my first mentors was Dick Bonin, the founder of Scubapro. I originally worked with him as his equipment distributor in the Virgin Islands. That company was called V. I. Divers, Ltd. And it grew into the largest diving operation in the eastern Caribbean. Bob Hollis started Oceanic, and we worked together on everything from filming wrecks to saturation diving to gear manufacturing. Stan Waterman and Hans Hass were my two overwhelming influences in photography and filming. Bev Morgan, the pioneer of modern commercial diving equipment, and I met first in the summer of 1967 when I was still in high school. It was amazing hanging out with him in both diving and surfing.

AMA: Becoming a member of the Explorers Club and being inducted into the AUAS Diving Hall of Fame are great honors… When did you receive them?

BG: I was inducted into the Explorers Club as a Fellow National in 1993, its highest honor. I was also voted into the AUAS Diving Hall of Fame in 2012 as a recipient of their NOGI Award. I’m truly grateful.

Gilliam surfacing from 2500ft dive, 1992
Gilliam surfacing from 2500ft dive
in deep submersible in 1992


AMA: "Exploration," as a pursuit, was once just for a select few. Now the word is sometimes abused in conversation. How do you interpret this concept?

BG: I have been involved in worldwide exploration for decades and had the privilege of working with so many amazing people. I have been a member of the Explorers Club for nearly 30 years and greatly admire the organization’s contributions. But there are a lot of folks out there that do not actually meet the criteria. It seems that many are more concerned with sewing a patch on their jacket or pumping up their supposed qualifications...

AMA: What are the “must-have” books for a dive library?

BG: The Silent World by Cousteau, anything by Stan Waterman, Sea Change by Sylvia Earle, Fifty Fathoms by Blancpain, Diving with Safety by Bev Morgan, and Silver Seas by Ernie Brooks.

AMA: What was your professional relationship with Tom Mount like? Can you describe how the masterpiece, Mixed Gas Diving: The Ultimate Challenge for Technical Diving, was born?

Deep Diving by Bret Gilliam
Deep Diving by Bret Gilliam

BG: Tom and I met in 1972 and immediately established a close relationship. Tom was one of the most skilled divers I had ever met, and we had so much in common. Ken Loyst of Watersport Publishing asked me to do a sequel to Deep Diving, and that was a bestseller, so we collaborated on Mixed Gas Diving.

AMA: When did you get the idea to study the physiology of oxygen and its effects in scuba diving theory?

BG: It was crucial to our survival to be able to manage the extreme depths we worked in and to have a full understanding of the potential hazards. There are many aspects of diving physiology that were complicated and presented special challenges. The management of the oxygen exposure and issues of oxygen toxicity were at the top of our list of hazards.

I was mentored by a diving medical officer who brought me in to run the Navy recompression chamber on the ship. This led to a six-month period with him covering virtually all foreseeable contingencies.

Oxygen was just one of our daily considerations in dive planning. Back in 1971, 50 years ago, we had to deal with so many subjects, which directly affected our dives, that it really concerned the ship’s officers. But we used our practical experience and accessed medical references to make certain that we could deal with narcosis, oxygen toxicity, high-pressure nervous syndrome (HPNS), work of breathing from the regulators at extreme depths and so many other issues.

Bret Gilliam operating recompression chamber for NOAA in 1988
Bret Gilliam operating recompression
chamber for NOAA in 1988


Again, back in that era, we routinely worked deep on air, and our standard PO2 limit was 2.0; that was modified to 1.6PO2 in the ’70s. But we needed to get deeper and switched to heliox below 300ft. Overall, we were completely comfortable with the dive plans we created, and the Navy was extremely pleased that we could get the filming done at such extreme depths.

There is no question that our project was extremely high priority due to the Cold War tactics of submarine operations. In essence, we were considered expendable. So, we concentrated on adapting our dive plans, equipment, decompression procedures and contingency planning to stay alive. We finished the project way ahead of schedule, and I was released from further military service. Fascinating times!

AMA: How have human factors influenced your technical thoughts on deep diving?

BG: The underlying science and physiology require both considerable practical experience as well as a full understanding of all the hazards and contingencies that deep divers must deal with. The primary issues involve inert gas narcosis and oxygen exposures to high PO2 levels. But you must carefully select the gear, the sites (drop-offs, caves, wrecks, etc), have a firm grasp on contingencies, understand the decompression models, and have a full attitude on situational awareness.

AMA: How do you see the future of scuba diving? Does open circuit have more to tell or is it dead?

BG: Actually, I see more of a trend to standard open circuit gear. It is well designed, reliable and affordable. Rebreathers have a place in many areas of diving, but they also are expensive for most divers, require extensive training and practical experience, and many specialty manufacturers have had trouble staying in business. I am all for innovations and technological advancements. But there has been a high incident rate for both injuries and fatalities within certain technical diving segments, and this needs to be recognized and resolved.

AMA: What is the future of TDI?

BG: TDI is doing extremely well… even in the pandemic economic turndown. The dive industry is in serious decline, but several companies have shown remarkable growth. TDI celebrated its 27th anniversary in 2021 and is continuing to grow.

Rutkowski IANTD
Dick Rutkowski developed the first
nitrox training courses when he
founded IANTD. Tom Mount, Billy
Deans and Bret Gilliam were all founding partners.

AMA: Hyperbaric medicine has grown up fast during the past few decades. You have been involved in this field for 50 years. Can you give us an overview of how hyperbaric medicine has influenced scuba diving from the past to the present day? How do you see the future of this field?

BG: The research and development of procedures and protocols in the treatment of divers has been extraordinary. And the knowledge and expertise of the hyperbaric medical experts have been equally distinctive. Working with guys like Dr Tom Neuman, Dr Paul Cianci, Dr Bill Shane, Dick Rutkowski and others was so valuable. I think so much has been accomplished that a new level of excellence has been achieved.

What worries me today is that so many hyperbaric facilities and field chambers have been shut down for financial reasons. The future is a bit unknown and how the diving medical treatments will emerge with far fewer hyperbaric facilities is a bit unnerving.

AMA: What does “freedom” stand for you? In relation to scuba diving practice, of course…

BG: My entire professional career was in diving, and I owned my companies, so I did not really have to answer to anyone. I tried to use the best judgment I could for training, safety, boat operations, etc, and allowed my diving customers the freedom to make their own decisions for diving based on experience.

Bret Gilliam in store, 1972
"We had several large custom dive vessels, a
retail store and training facility, and did location
film work for Hollywood movies, television shows
and documentaries. The company grossed a
million dollars in sales the first time in 1976."


Many dive operations were very restrictive and put rules in place that made no sense to well-experienced divers. My companies were different. We allowed decompression dives. We had no limits on depth. We allowed our diving customers complete independence based on our evaluations of their training and experience.

Many of our customers did three to five dives per day in an era when most divers were limited to one or two.

The Cayman Islands restricted all dives to 100ft or less—no deco, no nitrox, no dive computers, and your second dive could not be deeper than 50ft. All divers were herded into groups with no independent diving allowed at all. It did not make for a positive customer experience for most divers, and it drove thousands of divers to abandon the Caymans and other areas.

Waterman, Giddings, Nicklin filming The Deep, 1976
Stan Waterman, Al Giddings and Chuck Nicklin on location, filming The Deep in 1976

Freedom is good if such procedures and practices are well thought out and practical. It worked well for me and my companies. When I founded Ocean Quest International in 1988, we averaged nearly 1,000 dives a day with our customers. That’s over 4,000 dives a week. It was the largest dive operation in world history.

AMA: Al Giddings was the only American scuba diver on board the first Italian expedition on the Andrea Doria wreck. What was the professional relationship you had with him?

BG: Al and I met in 1971, and I became the distributor of his underwater photography line in the Caribbean called Giddings-Felgen. Great products! Then, I did some early movie work with him before we started work on The Deep in 1976.

The list of his movies that we worked on is amazing. Al was THE go-to underwater film guy, with such hits as The Deep, The Abyss, Titanic, Never Say Never Again, True Lies, The River Wild, and scores of documentaries and television series, including the ABC Ocean Quest series in the mid-1980s.

Cameron and Giddings, filiming Titanic, 1997
Director James Cameron and Al Giddings while filming Titanic in 1997

Al Giddings was editing the final underwater footage for Titanic, which would be released a few months later in 1997. We ended up at dinner with his neighbor actor Dennis Quaid that night at Al’s estate in Montana. Amazing man and a wonderful mentor!

AMA: A wreck is a symbol of a story. What does a shipwreck represent to you?

BG: There are multiple stories about ships and their initial sinkings. But I think the heritage of the wrecks is so important. I am fascinated by everything from WWII aircraft wrecks to merchant ships, submarines, warships, and ancient era underwater archeology.

AMA: Do you collect sea artifacts?

BG: Over the years, I have been lucky enough to find some wonderful artifacts, bottles, coins, treasure and jewelry, including gold bars in the Banda Sea in Indonesia.

AMA: Best wreck dives?

BG: My favorites are in the Solomon Islands, Truk Lagoon, Papua New Guinea, Bikini Atoll, parts of the Caribbean, and many of the deep wrecks right off the Florida coast.

AMA: Any missing wrecks to your wish list?

Humpback whale. Photo by Bret Gilliam
Humpback whale. Photo by Bret Gilliam

BG: Never had the chance to visit the Titanic!

AMA: If you had one choice, what would be your favorite dive?

BG: I started working with whales in the mid-’60s and have been emotionally attached to them ever since. My favorites are humpbacks. They have a friendly gregarious nature, and I love filming them. I freedive, holding my breath, for almost all dives. We found out, decades ago, that humpbacks do not like exhaust bubbles and simply disappear if you come anywhere near them.

But the whales seem thoroughly happy if I simply freedive with them. I can routinely hold my breath between three and four minutes and get down to 150ft or so. The whales get curious as to why a human is so deep and come over to check me out. I have been truly blessed over my life to spend so much time with whales all over the world.

AMA: What is the essence of scuba diving for you?

BG: I feel at home in the ocean and always enjoyed its tranquility. Every creature in the ocean is a friend, and I am awed by the natural beauty of the sea.

Great white shark, Guadalupe Island, Mexico. Photo by Bret Gilliam
While working with great white sharks off Guadalupe Island in Mexico, this 18ft, one-ton female swam up to Gilliam and posed less than three feet away while he was outside the cage. Photo by Bret Gilliam


Well, there you have it. You just got inside a world of wisdom, reaching the end of the extended version of the interview with Bret Gilliam. What have we learned from the past? This was the main talking point of the discussion I had with Gilliam, the revolutionary trailblazer who changed the way scuba divers dive, and think about diving, all over the world. So, I want to know: Have you ever seen the rain?

Based in Italy, author Andrea Murdock Alpini is a technical diving instructor for TDI, CMAS and ADIP. Diving since 1997, he is a professional diver focused on advanced trimix deep diving, log dives with open circuit, decompression studies, and research on wrecks, mines and caves. Diving uncommon spots and arranging dive expeditions, he shoots footage of wrecks and writes presentations for conferences and articles for dive publications and websites such as ScubaPortal, Relitti in Liguria, Nautica Report, SUB Underwater Magazine, ScubaZone, Ocean4Future and InDepth. He is also a member of the Historical Diving Society Italy (HDSI), and holds a master’s degree in Architecture and an MBA in Economics of Arts. He is the founder of PHY Diving Equipment (, which specializes in undergarments for diving, as well as drysuits, hoods and tools for cave and wreck diving. Among other wrecks, he has dived the Scapa Flow wrecks heritage, Malin Head’s wrecks and the HMHS Britannic (-118m), Fw58C (-110m), SS Nina (-115m), Motonave Viminale (-108m), SS Marsala (-105m), UJ-2208 (-107m) and the submarine U-455 (-119m)—always on an open circuit system. His first book, Deep Blue, about scuba diving exploration (in Italian) was released in January 2020 (see For more information on courses, expeditions and dived wrecks, please visit: