To be honest I thought the acting was pretty good. The only actor I didn't like in the movie was the guy from the Fantastic Four, I don't even know his name. It's one of those movies that you can't look at for a complete story line, but is packed with great scenes and life's lessons. If you take the underwater scenes from The Titanic, and The Abyss and multiply them by 100, that's what your getting in Sanctum.
Besides for the risks, being a caver/explorer/spelunker would be awesome!