The main story focuses on the fact that the cavers have to find a route to the sea or die when a cyclone moves in and blocks their ascent to the surface. It's a silly film that doesn't really use the 3-D tricks it purports to contain.
The fact that it's in 3-D got me thinking. Cameron does a lot of school films. If you ever take kids to a Science-cum-Nature museum you'll find an educational film of his playing in the IMAX there (if they have 1). They'll focus of fish, dinosaurs, the moon, space or caves. This film reminded me of off cuts from those films that have been strung into a story. Not good if a film is trying to grip you.