After a nuclear submarine mysteriously sinks in a remote part of the ocean floor, a team of divers on a prototype underwater oil rig are pressed into service by the U.S. Navy in a rescue attempt. When a hurricane cuts off contact between the surface and the underwater depths, the crew begin to see evidence of a strange, possibly alien intelligence at work. While Chief Bud Brigman (Ed Harris) bickers with his ex wife and boss (Mary Elizabeth Mastrantonio), the Navy commander begins to grow increasingly paranoid about the mysterious alien life and threatens to use a recovered nuclear weapon to destroy everything.