"Sink the Bismarck!" was made before 1975, when the British code-breaking at Bletchley Park was declassified, so it did not reveal that Shepard's hunches about the movements of the "Bismarck" were supported by intelligence. Direction finding and traffic analysis showed that on 25 May, "Bismarck" stopped talking to Wilhelmshaven and started up with Paris, and Shepard committed to the belief that "Bismarck" was headed for the French coast. The radio switch from Wilhelmshaven to Paris might have been caused by "Bismarck"s crossing the line southern Greenland – northern Hebrides which brought her under Group West instead of Group North. Nonetheless, Shepard's hunch was soon proved correct when, by good luck, a Luftwaffe Enigma transmission was intercepted and decoded at Bletchley Park, revealing that "Bismarck" was headed for Brest to repair an oil leak. The Luftwaffe Enigma code had been broken early in the war, unlike the German naval Enigma, which was only broken later and was subject only to traffic analysis during the "Bismarck" affair. Damage during its battle with HMS "Hood" and HMS "Prince of Wales" caused flooding that put "Bismarck"s bow barely above sea level, and oil slicks caused by hits from HMS "Prince of Wales" were apparent; in the film, "Bismarck"s bow remains at its normal height above sea level.