Cave diving expeditions have so seldomly become the object of action movies. The closest I can recall would be "The Descent", but even that one was in fact part of the survival horror genre. I guess caving just isn't that exciting in movies, without something to enhance the experience. So this is why, with the help of James Cameron (serving as executive producers), they tried to push "Sanctum" as the ultimate 3D cave dwelling experience.
The movie tells of the adventures of an expedition going into one of the largest unexplored cave systems in the world. A powerful storm rips through the area and floods the caves, trapping the group of explorers deep within. A race against the clock ensues to find a way out. And it would all be so exciting if it had but a few needful things, like interesting characters and dialogue, and good 3D. Indeed, this is where the movie suffers tremendously. The dialogue is so stale you can taste it in your mouth and the characters are so cliched that they just feel like stock characters used in place of real ones. And let's not go into the acting. What acting ? Richard Roxburgh does a pretty good job, all things considered, as Frank, an experienced cave diving veteran, and Rhys Wakefield shows some promis as his son, Josh. But everyone else just fades into the darkness of the cave. I was half hoping that the creatures from "The Descent" would jump in and eat them all. And everything that happens is so over-the-top from a dramatic point of view. We've got it all, from father-son issues to betrayals and sacrifices, and of course there's something rotten with the rich dude. Also, filling the dialogue with F-bombs, and pushing the violence to an R rating is just pointless and gratuitous, doing more damage than good.
But I'm being too harsh, I guess. The actual adventure stuff is pretty good. The sense of claustrophobia and suspenseful climbing scenes are pretty well done, although not as intense as, let's say, "Vertical Limit", or "K2: The Ultimate High". I guess I'm about to once more state that point about caving movies not being terribly exciting. But, like I said, it does have its moments. Word of warning though, if you intend on seeing this in 3D, don't. It's well known that 3D darkens the image considerably, and since most of the movie takes place inside a cave, most of it is already pretty dark, which renders the 3D useless. Some nice aerial views in the beginning show promise, but it's better to just go ahead and watch it in normal 2D.
It's disappointing that Cameron actually endorsed this movie. It's just not very good. The premise sounded good, and I guess the mirage of making this in 3D was rather tempting, but bad casting, a lousy script, inexistent direction and a lack of excitement sink this one. In the end it qualifies as passable entertainment, but if you're seeking some kind of exciting blockbuster, this is not it.