The Abyss and The Descent. I was quite wrong.
James Cameron was an executive producer on this film, again I was under the assumption that he directed this. I'm sure others were also since his name is at the top of the movie poster with this last film, Avatar, mentioned. Don't be fooled. This was directed bu Alister Grierson, and he hasn't done anything you've seen.
The film is about a group if scientists that are exploring a cave system that has never been accessed in the history of mankind. While deep in the cave a tropical storm hits. At their depth they have no sign of the storm, and the radio communication to the ground level are out. With no warning water starts to fill up the cave. They are forced to continue to the other side [e.g. - we know the water in the cave feeds a river].
The problem with the film is the horrendous acting. Father [Richard Roxburgh] and son [Rhys Wakefield] were not good, and bad guy Ioan Gruffudd wasn't any better. Wakefield reminds me of the Hayden Christensen in the Star Wars films.
Don't get suckered into watching this because they put Cameron's name on it.
IMDB Link: http://www.imdb.com/title/tt0881320/