After a collision with an unknown object, the American nuclear submarine USS Montana sinks to the bottom of the sea. The army sends a team of four specially trained Navy Seals on a rescue mission. Time is of the essence, as enemy submarines are on their way to the scene of the accident and a hurricane is approaching. Under the leadership of Lieutenant Hiram Coffey, the team, together with engineer Lindsey Brigman, embarks on an undersea drilling platform that will serve as a base for the mission. However, this not only leads to conflicts with Brigman's divorced husband, who runs the platform, but also the Navy Seals have difficulties dealing with the pressure situation. In addition, there is the mystery of the unknown object that reappears.