U-Boat Prisoner
"HITS HIGH-WATER MARK of ACTION!"
Merchant seaman Archie Gibbs manages to survive when his ship is torpedoed by a German submarine. Disguising himself in the uniform of a dead Nazi spy, Gibbs is picked up by the Nazi U-boat. He manages to convince the German sailors that he's the spy, and in this guise he tries to rescue a group of captured Allied scientists.