The nuclear submarine Montana experiences a problem while in the Cayman Trough. It comes up against something unknown that turns off it's power but the sub regains power and has moved close to a canyon wall that ruptures the sub hull. All crewman are dead, but it's the missiles that everyone is wanting. The Russians and the Americans are sending vessels to salvage the wreck but the American want to use a seal team on an underwater oil platform. The creator of the platform is furious and travels with the seal team. Lindsey Brigman (Mary Elizabeth Mastrantonio) heads down to the platform and runs into her estranged husband Bud (Ed Harris). Of course they immediately start to argue and don't notice that seal team leader Lt. Coffey (Michael Biehn) is having problems.
The team take a look at the Montana and while aboard they see the creatures that inadvertently destroyed the ship. Even Lindsey who has traveled to the Montana in a small submersible sees the creatures and even her lights go out when they are around.
On the surface a hurricane is kicking everything about. The underwater rig is feeling it also and moves closer to the edge of a precipice.
Lindsey and Bud have to travel in a submersible to see what they can do with the warheads. While down they come into trouble. There is only one suit that will take them to the platform. Lindsey tells Bud to put it on. She knows she will drown but she feels if Bud can get her back to the platform she can be revived. The water being as cold as it is should help her. Bud does get her back and they are able to revive her, one problem, they still have to take care of the warheads.
Bud puts on a suit that will fill with liquid and he will be breathing this in rather than air. It will allow him to go into the trench. On the way down, he notifies Lindsey that he knew it would be a one way ticket. I have to stop here, because to tell you anymore will ruin the movie for you.
Director James Cameron brings fantasy, terror and reality all into one for this movie. The ending is not what you thought it would be. This is a story that if you can have an open mind then reality doesn't seem so far off. This is a movie to sit and enjoy and wonder.