If you haven’t seen it already, one of the best diving-related documentary films of recent times started streaming in the UK and elsewhere towards the end of 2025.
The general public, if pressed, would be able to name very few scuba divers, but the self-effacing Richard ‘Harry’ Harris might be one of those few, thanks to his pivotal role in the 2018 Tham Luang cave rescue and the amount of coverage it received.
The Australian cave-diver, an anaesthetist by day, took responsibility for bringing the trapped young Thai footballers out of the flooded cave system by keeping them sedated on ketamine, and he and the team didn’t lose a single one of the boys.
The potential reputational damage had it been otherwise is not difficult to imagine, and most people would settle for such a feat in terms of lifetime achievements. However, in 2023 Harry undertook a deep cave dive that, while it might have meant less to the public, was a true milestone for technical divers.
He set out to dive 220m deep into an uncharted section of New Zealand’s Pearse Resurgence, using potentially explosive hydrogen to overcome the HPNS tremors and dense air effects that occur at such depths. It would be an unprecedented foray into a system that could prove to be the deepest dived cave in the world.
Thought processes
Deeper records the lead-up to the attempt, and it’s exciting, engaging and compelling. Not least among its appeals are the interactions between Harry and his team, notably his long-time buddy Craig Challen and dive-supervisor Dr Simon Mitchell.
The film offers an insight not only into elite cave-diving project management but also to the divers’ thought and decision-making processes and emotional engagement.
This 90-minute documentary is directed by BAFTA-nominated Jennifer Peedom, who made the extreme-sports documentaries Mountain and Sherpa, and is clearly fascinated by high and low places. It is distributed by Dogwoof, behind films such as The Rescue, the 2021 Tham Luang account and, back to rock-climbing, Free Solo. These people enjoy bringing invisible adventures into the light.
That can be the problem with cave-diving – one tunnel can look much like another, and the most remote solo penetrations have to rely on body-worn GoPros rather than the artistry of a film-crew.
That is not a factor in Deeper, however, because the interest is in the build-up and the fact that nobody, divers or film-crew, knew what was about to happen.
Tempting fate
“I’m definitely not a brave man,” says Harry, who says he found his niche in scuba after failing at sports as a teenager, and whose wife Fiona feels he is now tempting fate. “When I’m cave-diving I have never felt more alive,” he says.
Diving the Pearse Resurgence had been his obsession, and the Hydrogen Expedition with the impressive Wet Mules dive-team “the most dangerous thing I’ve ever attempted”. Deeper records his ninth dive there – the first had been in 2007 with established divers Rick Stanton and Dave Apperley.
Watching the former’s 177m dive to what is now Stanton’s Hole “changed my whole paradigm”, says Harry, who managed to get 5m deeper the following year. His Pearse explorations with Challen began in 2010 and, 13 years of underwater adventures later, they have formed a bond that is interesting to see come under pressure in the film.
“Technical diving is a lot better in the retelling than in the actual doing,” says Harry at one point. Don’t miss this retelling – Deeper is available to rent and buy on Prime Video, Apple TV and Sky Store.
