AllMovie

Versatile character actor Vito Scotti guest stars as a Japanese soldier who has been piloting the local waters in his one-man submarine for twenty years, unaware that WW2 is over. Bobbing to the surface, the soldier "captures" the island and takes the castaways prisoner, locking them in a makeshift jail booby-trapped with hand grenades. It is up to Gilligan (Bob Denver) to rescue his companions without getting blown up in the process.