Explorer Richard Harris, key in the Thai cave rescue, risks all diving NZ's potentially deepest cave system. As he pushes limits underground with limited air, he questions his motivations and impact on loved ones.
Jennifer Peedom’s documentary Deeper offers an intimate look into the world of extreme cave diving through the eyes of Richard “Harry” Harris. The film positions itself as both an adventure story and a character study, and it succeeds most strongly in the latter. At its core, Deeper feels like a personal tribute from Harris to the pursuit that shaped his life. It is a reflection on a hobby that grew into a calling and eventually propelled him into global recognition after the Thai cave rescue. The documentary explores this passion with sincerity, although its narrow focus sometimes limits its broader appeal.
The film follows Harris and his long time diving companions, known collectively as the Wet Mules, as they attempt to push deeper into New Zealand’s Pearse Resurgence. This cave system is considered one of the most challenging and potentially deepest in the world. The team’s 2023 Hydrogen Expedition forms the spine of the narrative. Their goal is to overcome High-Pressure Nervous Syndrome (HPNS), which causes tremors, confusion, anxiety, and cognitive impairment in dives beyond 150m. The team aim to test hydrogen as a breathing gas at extreme depths, a concept that is both scientifically fascinating and inherently dangerous. The divers are fully aware of the risks involved. Hydrogen can explode if mishandled and can freeze lung tissue if delivered incorrectly. The film acknowledges these dangers, although it often does so in broad strokes rather than detailed explanations.
Peedom presents Harris as a thoughtful and humble figure. He repeatedly insists that he is not a brave man, which becomes a recurring theme throughout the documentary. His modesty is genuine, yet it also highlights the paradox at the heart of the film. Harris is drawn to environments that most people would never willingly enter. He is compelled to push deeper into the earth for reasons he struggles to articulate. The documentary attempts to explore this internal drive, but the answers remain elusive. This ambiguity is part of the film’s intrigue, although it may leave some viewers wanting a clearer sense of motivation.
One of the challenges Peedom faces is the inherently uncinematic nature of cave diving. The underwater world inside the Pearse Resurgence is dark and visually limited. Visibility is often poor and the divers move slowly through narrow spaces that offer little for the camera to capture. There are no sweeping mountain vistas or dramatic cliff faces. There are no dangerous animals lurking in the shadows. The danger is real, but it is internal and technical rather than visual. As a result, the documentary relies heavily on surface footage, interviews, and drone shots of the surrounding wilderness to create visual interest. These scenes are beautiful, although they sometimes feel disconnected from the central action.
The film also leans on the Thai cave rescue as a narrative anchor. For viewers who are not familiar with deep diving, these flashbacks provide emotional context and help explain why Harris is such a respected figure. They also serve as a reminder that his greatest achievement is already behind him. The documentary never states this outright, but the implication is clear. The shadow of Tham Luang hangs over the entire film. Harris’s new expedition is important to him and to the diving community, but it does not carry the same global stakes. This contrast shapes the way the audience experiences the story. The tension is quieter and more introspective, which may not satisfy viewers expecting a high intensity survival narrative.
Where Deeper is most engaging is in its exploration of the scientific and physiological challenges of extreme diving. The divers discuss high pressure neurological syndrome, tremors, cognitive impairment, and the mental strain that comes with descending to such depths. These topics are fascinating, yet the film often touches on them only briefly before moving on. Many viewers will likely wish for more detail. The process of mixing gases, the calculations behind the chosen ratios, the methods used to prevent explosions, and the logistics of switching breathing systems mid-dive are all mentioned but not explored in depth. These are the kinds of insights that could have drawn non-divers further into the story. The fact that the audience had many questions during the post-screening Q&A suggests that the documentary leaves some of its most interesting material underdeveloped.
Structurally, the film sometimes feels stretched. The runtime is modest, yet the pacing can feel slow because so much time is spent on introductions and background information. The documentary could have benefited from a tighter focus on the Hydrogen Expedition itself. A deeper dive into the cave system, its history, and its unique geological features would have added valuable context. Instead, the film often returns to Harris’s personal reflections, which are thoughtful but occasionally repetitive.
Despite these limitations, Deeper has several strengths that keep it engaging. The relationship between Harris and Craig Challen is one of the film’s emotional anchors. Their camaraderie provides warmth and humour, which helps balance the seriousness of the expedition. Their interactions reveal the human side of extreme exploration. They joke, they worry, and they support each other in ways that feel authentic and relatable. These moments give the documentary a sense of heart that elevates it beyond a simple adventure chronicle.
Peedom also makes effective use of maps, communication logs, and underwater audio to help the audience understand the divers’ progress. These tools provide clarity in an environment that is otherwise disorienting. The sound design is particularly strong. The rhythmic hiss of breathing equipment and the muffled stillness of the cave create an atmosphere that oscillates between serenity and anxiety. These sensory elements help convey the psychological experience of deep diving, even when the visuals are limited.
Ultimately, Deeper succeeds as a thoughtful portrait of a man who is driven by curiosity and a desire to test the limits of his own capabilities. It is informative and often compelling, although it does not always deliver the level of tension or scientific detail that some viewers may hope for. The documentary is most effective when it embraces its introspective nature. It invites the audience to sit with the mystery of why people like Harris pursue such extreme challenges. The film does not provide a definitive answer, and perhaps it never could. Some motivations live too far below the surface to be neatly explained.
Deeper had its Aotearoa NZ Premiere on January 16, 2025.
Keep an eye out for additional screenings here