Paul Henreid's film debut.
The Finnish submarine "Iku-Turso" was used in some scenes. Ufa (the production company) also purchased the Finnish schooner "Maria av Viborg" to be blown up as the British U-boat trap in the battle scene.
The first film to be shot under the new Nazi government; it began filming just three days after Adolf Hitler took power in Germany.
The first German submarine movie after World War I.