SANCTUM has excellent 3D cinematography while the script loses some luster as it digs into the Hollywood cliché rulebook from time to time.   It is inspired by the true story of co-writer Andrew Wight (a diving buddy of director James Cameron) where he once went cave diving with 14 people and became trapped (which was documented in the documentary film NULLARBOR DREAMING).  They had to find another way out and they all lived. 

However, SANCTUM doesn't have the same rules.   It has all of the stereotypes lined up from the great cave diver who is too hard on his son and the billionaire who needs something to spend his money in (and get his thrill junkie addiction fed).   Everyone ignores the impending storm and don't pack things out until it is too late and a group of the expedition gets trapped and they have to find another way out.   Like in a movie, some of them probably won't make it out alive, but I wonder if they needed the body count to make a thrilling movie.   As they dive into the stereotypes and book of screen writing cliches, the movie does loose some of it's strength and only the wonderful cinematography (and some good direction) holds it together.   You have some good actors in it and yet the movie has something against the female characters (as it goes out of its way to put the women through pain and panic).