DEEPLIFE in Diving Hyperb Med (2025)

Deep diving presents significant physiological challenges for humans. The recent rise of closed-circuit rebreathers has enabled more divers to reach unprecedented depths. The present study, conducted by Emmanuel Gouin, diver and expedition doctor with Under The Pole, in collaboration with the medicine and physiology team involved in the CAPSULE program, explored the physiological limits and challenges of extreme deep diving and the strategies developed to overcome them.

This study is based on the experience of deep divers. Eight rebreather divers (one woman, seven men) with experience beyond 200 meters depth were interviewed about the preparation, planning, and execution of such dives. The profiles of their deepest dives were analyzed. All were highly experienced divers, with dives ranging from 209 to 302 meters depth.

The results show that the gas usage procedures (gas density, ppO₂) and decompression procedures (ascent rates) often do not follow current recommendations in order to reduce decompression time. Indeed, decompression for the deepest dives could last over 10 to 15 hours, exposing divers to additional risks such as cold, dehydration, and fatigue. However, deviation from these recommendations led to decompression sickness in three of the eight divers after their deepest dives.

The study highlights the uncertainty surrounding adherence to deep-diving standards and emphasizes the importance of rigorous dive preparation, the use of rebreathers suitable for extreme deep diving, surface support, and the technical skills of divers to reduce risks—which remain excessively high in deep diving. The use of a dry underwater habitat could improve divers’ decompression conditions (allowing them to eat, drink, stay dry, etc.) and encourage compliance with the inevitably long decompression periods.

Summary from the article "Extremely deep bounce dives: planning and physiological challenges based on the experiences of a sample of French-speaking technical divers."

Read the full article via the link below. 

Authors - Gouin E, Dugrenot E, Gardette B.