German U-Boats in action: shots of conning tower of U-Boat, crew on tower. CU of officers. Long sequence on U-Boat leaving port, sailing on surface as seen from another boat, from connning tower of camera boat, of bow of submarine smashing through swell. An allied freighter is spotted (seen through circular mask), crew race to stations. Cut to depth gauge, crewmen manning posts. LS of three torpedo explosions in distance. Cut back to gauge showing surfacing, crew racing to deck gun, firing it LS of explosion on freighter. Several shots taken from conning tower of bow of sub smashing through water.