"Deeper" (2025)

[Duncan Price]

"Deeper" is the story of the 2023 deep dive in the Pearse Resurgence undertaken by Richard "Harry" Harris and Craig Challen. The exploit is remarkable for the pioneering use of hydrogen as a diluent in the breathing gas used by Harris to mitigate high pressure nervous syndrome at extreme depths. The 87 minute production directed by Jennifer Peedom recounts the background to the exploration of the cave, including footage of Rick Stanton's 2007 dive to -180 m on his homemade rebreather. That cave rescue in 2018 also features as part of the narrative and it is interesting to learn that the Australian's reaction to the publicity surrounding the event was literally to try to hide underground until the media interest had subsided. Out of necessity, a lot of the footage is surface shots and talking head interviews with those involved which to be honest is more interesting than a video of swimming through the cave. The dialogue is refreshingly candid about the participants feelings about the venture (which was something I could indentify with) and I raised a smile at the team's three "rules" which I'll leave you to discover by watching it yourself. It's available to rent (£4.99) or buy (£9.99) on Amazon and the trailer can be found online.

Deeper - Official Trailer

 

[jonnybellman]

I think it might be the first and only thing I've ever paid to watch on Amazon. Certainly worth a fiver of anyone's money it's a great watch

 

[mrodoc]

To clarify things slightly hydrogen has been used as a diluent for many years but this was probably a first for its use in cave diving. I remember seeing a film on the Comex projects seeing the late Dr. Maurice Cross looking very depressed after a spell in saturation using hydrogen. If anybody is at all interested see (amongst many other things) https://trid.trb.org/View/434187

 

[jonnybellman]

To clarify things slightly hydrogen has been used as a diluent for many years but this was probably a first for its use in cave diving. I remember seeing a film on the Comex projects seeing the late Dr. Maurice Cross looking very depressed after a spell in saturation using hydrogen. If anybody is at all interested see (amongst many other things) https://trid.trb.org/View/434187

I think this is the first time it's used in CCR in any environment if I'm not mistaken. Either way, still cutting edge stuff

 

[David Rose]

I'm afraid I thought it was a poor film. There was almost no context: why the Pearse resurgence is so interesting, as the resurgence for New Zealand's deepest cave; the whole background of technical diving and mixed gas development; the divers' previous experience apart from the Thai rescue - and instead, an attempt to create a "success snatched from the jaws of failure" narrative that didn't ring very true. And at the end of the day, while the viability of hydrogen was demonstrated, they didn't explore very much.

 

[Duncan Price]

I viewed it in a different light. The location was incidental to the film's premise - that of a pair of cave divers experimenting with a novel approach to handling the physiological problems associated with deep diving and their candid feelings associated with the enterprise. It mirrors Rob Parker's 1985 deep dive in Wookey which was the first use of Trimix in a UK cave dive. During that push the team spent a week underground and Rob extended the cave by only a few metres on a dive that has been repeated several times since as a day trip. Harris & Challen subsequently repeated their use of hydrogen in Boesmansgat (South Africa) resulting in Harris suffering decompression sickness. I'm afraid that the divers' experience in Thailand will always follow them around and it would be the "elephant in the room" if it wasn't covered. I accept that it would have been great if more cave had been explored, but it wasn't the goal of the expedition, didn't happen and the film isn't about that. I understand that the team is not planning to return to the Pearse Resurgence.

I'll admit that I enjoyed the film because I know the people involved and enjoyed hearing them discuss how they felt about the enterprise - something I found refreshing and also something that I could identify with.

 

[David Rose]

Fair points, Duncan. But a film needs to appeal to an audience wider than the friends of its subjects. I thought an opportunity to engage that wider audience in the thrilling, contextual story of the Pearse and its feeder systems and the history of technical cave diving was missed.

 

[mrodoc]

I suspect the future of cave diving will increasingly rely on recce's with autonomous robots. This would allow the feasibility of dives to be assessed as well as permitting dive planning.

 

[Duncan Price]

Fair points, Duncan. But a film needs to appeal to an audience wider than the friends of its subjects. I thought an opportunity to engage that wider audience in the thrilling, contextual story of the Pearse and its feeder systems and the history of technical cave diving was missed.

I accept that - I should have qualified my remark by adding that I also enjoyed the film because I know many of the participants rather than this being the sole reason. Having said that, there can hardly be anyone interested in the topic that wouldn't be attracted to watch it due to the fame/notoriety of the principal divers. I think the approach taken by the producer was to focus on the human side of the expedition rather than the historical story of the cave itself - which is bound to disappoint some. By the time the film was released, the outcome was known and all three rules of the Wetmules diving team were not broken (you'll have to watch the film to find out).

 

[Lankyman]

I suspect the future of cave diving will increasingly rely on recce's with autonomous robots. This would allow the feasibility of dives to be assessed as well as permitting dive planning.

I've never been a diver just an interested observer but I was wondering about this. Would this be the underground equivalent of pre-inspection in rock climbing (a veritable minefield of unofficial rules and ethical stances!)? Would the use of a ROV take away from the fun of 'boldly going' into the unknown?

 

[Duncan Price]

-- Would the use of a ROV take away from the fun of 'boldly going' into the unknown?

ROV's have been used to explore a number of deep underwater caves - Fontaine-de-Vaucluse (-308 m), Zacatón (-319 m), Pozu del Merro (-392 m), Hranice Abyss (-450 m) (for example - depths are given from water surface to deepest point reached). I imagine there's a certain amount of fun avoiding the risk and monotony of deep cave diving by getting a robot to do it for you. It's not about ethics more about practicalities. There's a point where the danger exceeds the desire. The film illustrates this.

There are old cave divers and bold cave divers but no old bold cave divers.

 

[David Rose]

Except Jason... not that he's very old!

 

[Lankyman]

ROV's have been used to explore a number of deep underwater caves - Fontaine-de-Vaucluse (-308 m), Zacatón (-319 m), Pozu del Merro (-392 m), Hranice Abyss (-450 m) (for example - depths are given from water surface to deepest point reached).

Have those depths been reached by humans or by ROV (or both)?

 

[Duncan Price]

Have those depths been reached by humans or by ROV (or both)?

Deepest cave dive by a human: -312 m (2024): Xavier Méniscus at Font Estramar. Fontaine-de-Vaucluse has been dived to -250 m (Pascal Bernabe) , Zacatón -282 m (Jim Bowden), Pozu del Merro -223 m (Krzysztof Starnawski), Hranice Abyss -225 m (Krzysztof Starnawski).

 

[Lankyman]

I know the parallels have been made before but it does seem like the exploration of outer space where machines are going where people cannot go (at least for now). I read the account of the deepest dive at Estramar and it was fascinating.

 

[spelfish]

Presumably there's a depth below which a human (no matter what they breathe) cannot go unless they're encased in a pressure suit. Therefore the deepest cave dives will have to be made either by humans in submarines or by ROVs?

 

[Steve Clark]

The physical depth/pressure limit for a human is enormous. Comex did some saturation dives in a chamber at 701m. And in open water in the sea ‘working’ at 534m.

700m is 70bar / 1000psi.

That’s a serious depth for even ROV hardware to operate at. Probably about double the operating depth of most nuclear submarines.

 

[tdobson]

I thought an opportunity to engage that wider audience in the thrilling, contextual story of the Pearse and its feeder systems and the history of technical cave diving was missed.

The curse of knowledge [from the perspective of a professional communicator/storyteller]!

 

[Boy Engineer]

I'm afraid I thought it was a poor film.

I thought it was a fabulous film. It works on (no pun intended) so many levels. The challenge, the psychology of the individuals and the relationships between them, was eminently watchable, and had this viewer gripped. As The Guardian would say, 5 stars.