We're in the Navy Now (1926)

"Stinky" Smith makes off with the prize money when his buddy, "Knockout" Hansen loses a fight with Percival "Sailor" Scruggs. Hansen pursues him him a U.S. Navt recruiting office, and, the next thing they know, both are in the Navy and aboard an overseas transport ship. Madelyn Phillips is on board and Scruggs is the the ship's Master-of-Arms. They overhear a mysterious conversation between Madelyn and the ship's radio officer. Later, Madelun induces the pair to take her off the ship and into a row boat. She disappears and they are picked up by a French ship, which sinks a German U-Boat. When the war ends they learn that Madelyn was an operative of the U.S. Secret Service.