During World War II, Lieutenant Commander Quinton McHale (Borgnine) is the commanding officer of the U.S. Navy PT boat "PT-73," stationed at the Pacific island base Taratupa. In the late spring of 1942, the Japanese heavily bomb the island, destroying the base. Only 18 of 150 naval aviators and marines on the base survive. With Japanese patrols in the region too heavy for a Navy rescue mission, McHale and his men survive by hiding on the island. Assisted by the native tribes whom they befriend, the sailors live a pleasant island existence. After months of leisurely life, strait-laced, by-the-book Annapolis graduate Lieutenant Durham (Ron Foster) parachutes onto the island. His job is to assume duties as McHale's executive officer and help him get the base on Taratupa back into action.