Several months after the U.S. entry into World War II, an inexperienced U.S. Navy commander must lead an Allied convoy being stalked by a German submarine wolf pack.

A German submarine is boarded by disguised American submariners trying to capture their Enigma cipher machine.

A crew, drilling offshore for oil south of Jeju island, finds a lethal alien life form instead.

Strange happenings occur on a WW II submarine.