Safety
The Blueprint still holds
In 1979 Sheck Exley looked at why cave divers died and found the same few mistakes again and again. More than forty years later, his list still explains most accidents.
Technical diving · cave · wreck · trimix · CCR
Past the recreational line, the plan is yours.
A reference for practising tech divers. Where the community agrees, we say so. Where it doesn't, we set the positions side by side and let you weigh them.
TX 18/45
- O₂
- 18.0 %
- He
- 45.0 %
- MOD
- 67 m @ ppO₂ 1.4
- Analysed
- by the diver who breathes it
Every cylinder, every dive.
Read this firstInformation, not instruction. Nothing here replaces training with a qualified instructor.
Featured
Safety
The Blueprint still holds
In 1979 Sheck Exley looked at why cave divers died and found the same few mistakes again and again. More than forty years later, his list still explains most accidents.
Safety
Managing the risks you chose to take
Safety
Rule of thirds or minimum gas?
Two ways to decide how much gas to keep in reserve. One is simple and proven in caves. The other is calculated for the dive. Here's how each works, with a worked example.
Safety
Deep stops after the NEDU trial
For years, stopping deeper was thought to be safer. A 2011 US Navy trial challenged that, and decompression practice has been shifting since. What the evidence says, and what it doesn't.
History
How we got past 4o meters
History
From Haldane to Bühlmann
The decompression model in your computer has a family tree going back more than a century. A short history of how we learned to come up.
History
Sheck Exley and the rules of cave diving
The most influential cave diver of his era set depth records, wrote the rules that still save lives, and died pursuing a 1,000-foot dive. A profile.
History
Helium: how a rare gas opened the deep
Nitrogen made deep diving on air dangerous and unpredictable. Helium changed that, first for navies and oil companies, then for technical divers.
Locations
Sites that define the discipline
Locations
Chuuk (Truk) Lagoon: Technical Diving the Hailstone Fleet
More than 50 WWII wrecks from 3 m to 64 m, a volunteer-run chamber and a 2025 oil leak. What technical divers need to know before diving Chuuk's Hailstone fleet.
Locations
Émergence du Ressel
A river resurgence in south-west France that has drawn cave divers for decades. Shallow galleries lead to deep shafts, and the dive can be as simple or as serious as you make it.
Locations
Chuuk Lagoon
A Japanese fleet sunk in 1944 lies in the warm water of a Micronesian lagoon. It's one of the world's great wreck-diving destinations, and one that deserves respect.
Gear
Configuration is a set of trade-offs
Gear
Backmount, sidemount or CCR?
The platform you choose shapes almost every other decision about your diving. What each one does well, where each one struggles, and how divers choose.
Gear
Standardised or personalised?
Should every diver on a team use exactly the same configuration, or should each diver adapt their kit to themselves and the site? One of the longest-running arguments in technical diving.
Gear
Long hose or octopus?
How you donate gas to an out-of-air diver affects how you both get out. The long-hose method dominates technical diving, but it's not the only option.