The 3D thriller Sanctum was vaguely inspired by a 1988 flood that trapped co-writer Andrew Wight and 13 other divers in a cave. But no one would ever mistake the film for a true history: From start to finish, it’s a rigidly formulaic disaster picture, melded with the form of a coming-of-age story. There’s the quick introduction to the players, their relationships, and the layout of the gigantic, partially unexplored, partially underwater cave system they’re exploring. There’s plenty of foreshadowing and faux-offhanded introduction of information and elements that will—surprise!—become crucial later on. There’s an early crisis that lets everyone show their true colors, and a major crisis that traps them together in the cave system, with the goal of finding their way down to the sea in order to survive. And then there are deaths, polarizing conflicts over decisions, terrifying life-or-death struggles, and catharsis, all doled out at intervals as precise as the steps to a familiar dance.
Still, while Sanctum is frustratingly familiar, it’s easy to get caught up in the action. Produced by James Cameron, and filmed via the same proprietary 3D camera system he used for Avatar, it’s full of stomach-clenching settings, from vertiginous drop-offs to claustrophobic squeezes. Once the story enters the cave, the film is often Disney-documentary beautiful. The focus on the limits of the human body and the obduracy of stone and sea is unbeatably visceral, and Australian director Alister Grierson lets viewers feel the oppressive potential lethality in every slippery surface, sharp edge, steep drop, or wave of freezing water.
Whenever the peril level drops, though, Sanctum feels pro forma. Rhys Wakefield stars as the reluctant, sulky 17-year-old son of Richard Roxburgh, a gruff world-class cave-diver with little interest in the surface world. When the two reunite in a Papua New Guinea cave complex, along with Roxburgh’s ultra-rich, thrill-seeking boss Ioan Gruffudd and various other employees and partners, Wakefield and Roxburgh bark at each other just enough to establish a long-held mutual resentment that can be satisfyingly reversed when the going gets rough. The disaster-movie formula is flexible enough to leave some question open about who will survive at the end, and the filmmakers make every death hurt, and every survival a relief. If only the rest of the story was as hard to predict, or as emotionally involving.