When the German U-Boat surfaces near the U.S. coast, it is attacked by American bombers. The first two shots of the stock footage utilized show the attacking aircraft from the sub commander's view, the first through binocular- boxing on screen, are a trio of Lockheed Hudsons. But the overhead shot of the attack shows three Martin PBM Mariner flying boats, and then bombs are shown dropping out of a bomb-bay which the PBMs did not have.
Early in the film, a building in Berlin is shown with a sign that says "Abteilung Geheimdienst", which means "Secret Service". However, it was translated in the film as "Naval Intelligence". A more appropriate sign would have read "Marine Nachrichten Geheimdienst".