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GUE and the Future of Open Circuit Tech Diving

Though they were late to the party, Global Underwater Explorers (GUE) is leaning forward on rebreathers, and members are following suit. So what’s to become of their open circuit-based TECH 2 course? InDepth’s Ashley Stewart has the deets.



By Ashley Stewart. Header image: GUE CCR divers checking their values before they splash in Maple Bay, British Columbia, Canada. Photo by Andrea Petersen.

Is deep open circuit diving on the way out?
Is deep open circuit diving on the way out? Photo courtesy of GUE archives.

Neal Pollock’s piece in this month’s issue — “Will Open Circuit Tech Diving Go the Way of the Dinosaur?” — has us wondering: What does Global Underwater Explorers, a leading technical diving organization and the publisher of InDepth, think about the future of OC diving? 

GUE still offers training for open circuit dives to 75 meters/246 feet (and certifies divers at even greater depths after more experience) but has appeared in recent years to trend largely toward closed circuit rebreathers for longer and deeper dives. Just a few years ago, GUE reimagined training for closed circuit rebreathers (CCR), splitting the program into two classes and removing the requirement for divers to take the organization’s deepest open circuit class before embarking on the path to rebreather diving.

GUE Chairman Jarrod Jablonski believes “anyone doing anything of merit” will prefer rebreathers. While short, shallow recreation dives may continue on open circuit, CCRs provide significant benefits, such as safety and flexibility, particularly for dives greater than 20 minutes at depths beyond 80 m/260 ft. Pollock’s piece details the safety arguments for CCR, but there are practical benefits that come as no surprise to anyone who has seen the gas bill at the end of an open circuit trimix dive or tried to plan for tank logistics.

No bubbles to disturb the wildlife.
No bubbles to disturb the wildlife. Photo by Myra Wisotzky.

Take GUE’s project at Sweden’s most famous shipwreck, Mars the Magnificent, where the typical dive profile is 77 m/250 ft with a 40-to-50-minute bottom time. 

“One open circuit diver on the Mars project would consume more gas than 12 CCR divers combined,” Richard Lundgren, a GUE board member who ran the Mars project and started building GUE’s CCR program in the late aughts, told InDepth. Open circuit diving is therefore uncommon when it comes to projects of greater depths, Lundgren said, such as within and beyond the range GUE trains divers in “Tech 2,” from about 51 m/170 ft to 75 m/246 ft. There are still a lot of open circuit projects, Jablonski said, but they’re generally in the range of 40 m/130 ft, or shallower. 

Inside the wreck of Mars the Magnificent in the Baltic Sea.
Inside the wreck of Mars the Magnificent in the Baltic Sea. Photo by Kees Beemster Leverenz.

So why does GUE teach open circuit at these depths? Jablonski sees value, “for the time being,” in GUE’s current Tech 2 class. “For one,” Jablonski said, “some divers prefer to move more gradually toward rebreathers, or may want to explore and confirm an interest in deep diving before they make the significant investment in CCR.”

Plus, open circuit experience, Jablonski said, remains useful since the failure mode for most rebreathers remains open circuit. “All divers should have some experience with gas consumption and ascents on open circuit,” he said.

Lundgren, meanwhile, thinks of the call as necessary only for divers who are not eager to use rebreathers. “The skills and procedures acquired in the Tech 2 class are embedded in the CCR 2 class and, as such, is not a necessary step in the development,” Lundgren said. T2 enrollments have remained at a steady number, despite being removed from the pathway to CCR. GUE class enrollment trends, Jablonski reported, are showing CCR divers are trending toward CCR2 while RB80 semi-closed rebreather divers are still following the pathway of Tech 2 to rebreather. 

GUE has yet to publish its 2021 annual report, but the organization provided data to InDepth showing CCR1 enrollments were 2.5 times more than Tech 2 enrollments last year.

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Dive Deeper

InDepth: The Thought Process Behind GUE’s CCR Configuration by Richard Lundgren

InDepth: How GUE’s Approach to Rebreather Diving Compares to My Previous Courses by Andy Pilley


InDepth Managing Editor Ashley Stewart is a Seattle-based technology journalist and GUE Tech 2 diver.

Reach her via email:, Twitter: @ashannstew, or send a secure message via Signal: +1-425-344-8242.


The Art of Risk: What We can learn from The World’s Leading Risk-Takers




One of the rescuers of the Thai soccer team (now the Netflix series ‘Thai Cave Rescue’) and former Australian of the Year explores why people are attracted to risky pursuits and what we can learn from their expertise. 

In June 2018, with the eyes of the world watching, Dr Richard Harris, or Harry to his mates, dived into a remote cave in northern Thailand in an attempt to rescue a Thai youth soccer team who had become trapped by flash flooding. He used his recreational skills in diving to traverse kilometres of the subterranean cave system, and his professional skills as an anesthetist to sedate the stranded boys so they could be dived and carried to safety. Despite incredible odds, all twelve boys, along with their coach, survived. 

Harry says he was able to succeed in the Thai cave because of decades of experience, comprising thousands of hours of careful planning, risk assessment and management. Often described as the most dangerous sport in the world, Harry never feels like he is doing anything particularly dangerous when he goes cave diving. Despite losing friends to the sport, in his mind the risks can be managed well enough to make the pastime extremely safe. And far from making him anxious or fearful, the planning and execution of potentially high-risk dives have been empowering and fulfilling. In his mind, carefully managed risk-taking gives him the courage to manage the day-to-day stresses of life in the 21st century.

In The Art of Risk, Harry talks to like-minded risk-takers about their adventures and asks them what is it about cheating death that makes them feel so alive. He aims to explore the active pursuit of risk through the lens of risk-takers and adventurers such as soldiers, pilots, mountaineers, rock climbers, deep-sea divers, sailors, big-wave surfers, firefighters, rally-car drivers – both professionals and amateurs. His conversations give us insights into what motivates these people and why a life without risk is no life at all. He believes that by doing ‘the hard things’ in life you can push yourself a little harder and become stronger, more courageous and resilient.

Selling Points

  • FASCINATING SUBJECT: why do deep-sea divers, free climbers and big-wave surfers take the risks that they do? How do soldiers and firefighters manage risk? What can we learn from how they prepare – and what they experience – that we can take into our own lives? Harris shows that in doing ‘the hard thing’, we become more resilient and courageous. Angela Duckworth’s Grit meets Alex Honnold film ‘Free Solo’
  • EXPERT AUTHOR: Dr Harry Harris was at the heart of the Thai Caves rescue, anesthetizing all the boys in order to get them out. A genuine hero and former Australian of the year, Harry Harris explores flooded caves deep underground for fun. For most people, this is the definition of a nightmare. Because Harry understands and can prepare for the risks, for him it’s a pleasurable – even meditative – experience. And, as he says, he feels ‘carefully managed risk-taking gives him the courage to manage the day to day stresses of life in the 21st century’.
  • FAMOUS INTERVIEWEES: Harry talks with people like climber Alex Honnold, sailor Jessica Watson, mountaineer James Scott, film director and deep-sea diver James Cameron and polar explorer Tim Jarvis, amongst many others. 
  • MAN BEHIND THE NETFLIX SERIES: ‘Thai Cave Rescue’ is fresh onto Netflix, further pushing awareness of the story.

The Book

Publication date: July 2023
288 Pages plus color inserts

The Author

Dr Richard ‘Harry’ Harris, SC, OAM and joint 2019 Australian of the Year, is an anaesthetist and cave diver who played a crucial role in the Tham Luang cave rescue in northern Thailand. He has more than thirty years’ experience as a cave diver and also works for the South Australian Ambulance Service’s medical retrieval service. He is the co-author, along with Craig Challen, of Against all Odds, the inside account of the Thai cave rescue and the courageous Australians at the heart of it. He lives in Adelaide, Australia.

  • Halcyon Sidemount
  • Fourth Element
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