Who's that girl waving a semaphore message of "I Love You" to a destroyer as it departs New York for World War I? It's Sally, the Coney Island saltwater-taffy girl. Each of the sailors - especially pals and romantic rivals Baltimore Clark, Dutch Herman and Skeets O'Reilly - hopes the message is for him. But rivalries end where warfare begins. The pals are soon assigned to the crew of a merchant ship posing as a German communications boat. The mission: rendezvous with U-boat captains and learn their plan of attack. Bill Boyd, Robert Armstrong and James Gleason play the three friends. And who's that girl? It's captivating 20-year-old Ginger Rogers, two years before she and Fred Astaire would go Flying down to Rio.