When the USS Montana, a submarine carrying nuclear warheads, inexplicably collides into a sea wall and sinks to the bottom of the ocean, a deep-sea oil operation team is called upon to assist with the search and rescue. Led by Virgil “Bud” Brigman (Ed Harris), the drill team is partnered with a squad of Navy S.E.A.L.S. whose orders may not be as transparent as they seem. Bud’s hard-edged, estranged wife, Lindsey Brigman (Mary Elizabeth Mastrantonio), is also brought on board to lend her expertise as the designer of the massive underwater drilling rig. Upon reaching the Montana, the divers encounter something out of this world, an apparently new species of aquatic life, which they dub “N.T.I’s,” or non-terrestrial intelligence. While the team of civilian divers views these life forms as the discovery of the century, S.E.A.L. team leader Lieutenant Hiram Coffey (Michael Biehn) sees only a threat that should be eliminated by any means necessary. However, the hurricane gathering strength on the water’s surface may prove to be the greatest adversary of all.