Starring Richard Roxburgh and Rhys Wakefield. Rated 14A. Opens Friday, February 4

Sanctum goes deep with its stunning 3-D underwater camera shots, but, sadly, not with its characters. So although you get ethereal images of tiny divers floating amid giant stalactite-toothed caverns, the script falls somewhere close to being Poseidon Adventure with scuba gear and caving helmets.

There are still many thrills per minute in this Aussie disaster film—executive-produced by James Cameron—thanks mostly to the fact that it plays on primal phobias of small spaces, the dark, and drowning. Very loosely inspired by coscreenwriter and producer Andrew Wight’s real caving mishap, this story of underwater spelunkers caught miles below the earth in a labyrinth under New Guinea puts its adventurers in a nonstop stream of peril. Think suffocating scuba scenes, passageways so tight the swimmers have to carry their oxygen rigs in front of them, and pummelling waterfall climbs. And there’s an almost laughably gruesome body count to match—including the odd mercy killing for those too weak to keep up with the head hard-ass, Frank (Richard Roxburgh). This is the movie that should be called The Expendables.

Roxburgh is solid as the crusty caver, but like the other characters, Frank is prone to stating the obvious (“This cave isn’t going to beat me!” “This cave’ll kill you in a heartbeat!”) He spends the movie knocking heads with his 17-year-old son (Rhys Wakefield) and his business partner (Welsh actor Ioan Gruffudd as an overblown caricature of an adventure-seeking American billionaire who’s funding the mission).

The man-against-man stuff just doesn’t live up to the man-against-nature struggles here—nor to that other movie about getting trapped under rocks, 127 Hours. And for all its high-tech camera work, a system supposedly six years in the making, the terrible sense of dread that built in the comparatively low-budget caver The Descent isn't present. Still, those other films don’t have scuba divers swishing through the awesome depths of sea caves—not exactly an activity about which most of us can say “Been there; done that”.