Sanctum is the case of a movie that tries to do too much, without realizing what its real strengths are.
Directed by Alister Grierson from a script by John Garvin and Andrew Wight, Sanctum has as its marquee draw the name of its executive producer: James Cameron. Cameron's actual involvement? Who knows? But having his name on the film leads people to believe it's in some way his film, when, really, being an executive producer is often about as relevant to a film's quality as being a critic whose quote is used in the film's ad. Still, Cameron's own specially developed digital 3D process - which he created for Avatar - is used here.
Not that this movie needs 3D, except to pump up the bottom line. In fact, Sanctum doesn't need half the things the writers have thrown into the script. But they're there anyway, diluting the movie's power and distracting from its true source of excitement.
"Inspired" by a true story, the film is set in Papua, New Guinea, which the film's resident blowhard, Carl Hurley (Ioan Gruffudd), proclaims as the last unexplored frontier in the world. And on that island, the central squad's destination is even more forbidding: Esa'ala, a mammoth hole in the ground that is the gateway to a deep series of caves that ultimately lead underwater and back up to the surface.
Carl, a reckless billionaire adventurer, has financed an expedition by an expert spelunker and diver named Frank McGuire (Richard Roxburgh), to chart the unexplored portions of Esa'ala and discover a previously uncharted route through Esa'ala and back to the ocean coast. Frank and his team are using rebreathing diving equipment but, even so, they're so deep even before they get in the water that they have to go through considerable decompression to avoid the bends (which, as one of Frank's assistants notes, is when your blood begins to "fizz like a shaken can of beer").
That's part of the setup. The other is that Carl has come to help Frank make the final push to find the missing tunnel and he's brought his mountain-climbing girlfriend, Victoria (Alice Parkinson). Joining him on the descent to the underground base camp is Josh (Rhys Wakefield), Frank's rebellious teen-age son, who looks like Justin Bieber, if he grew a foot without sprouting body hair. Oh yeah - and there's a big tropical storm coming, which will flood the whole cave system, so Frank and crew have to climb back out of the hole before that happens.
Think they do? Of course not. Which means that a half-dozen of them are trapped underground and have to find an alternate route to the surface. Will they all survive? If you think so, then you would fail Disaster Movie Math.
The secret of Disaster Movie Math, of course, is that it's all subtraction. The fun is in guessing who will be subtracted and in what order.
Unfortunately, the writers and director want to complicate the equation.