Submarine warfare: AERIAL SHOT of corvettes hunting U-Boats. Boating shots of exploding depth charges. FOLLOW SHOT of captured U-Boat crews being marched past the camera for transportation to concentration camps. Sequence on British submarine sidling to supply ship, submarine being supplied with torpedoes, crews moving back and forth between the two ships. Vertical LAS of sailor coming down from hatch, closing hatch, as submarine prepares to move off. Interior shots of British crew in submarine. LS of silhouette of the submarine traversing frame. The submarine is either the Clyde or the Severn. AERIAL SHOT and BOATING SHOTS of submarine running on the surface. MS of prow cutting through the water. LS of submarine starting to submerge. HAS from conning tower, of front of submarine dipping under the water as the submarine submerges. Interior shot of conning tower, engine room, control room, with brief cut to periscope disappearing below the surface of the water. Shot of officer looking through periscope and cut to upper part of periscope going under water surface. HAS from the conning tower of the front of the submarine rising. Cut to LS of the whole submarine surfacing. HAMLS of the stern torpedo tube firing a torpedo from the surfaced submarine. LSs and HASs from conning tower of the submarine firing the deck gun. LAS of Skull and Crossbones flag.