Corrected entry: After the sub has hit bottom while attempting to pass through Gibraltar, the captain leans in to examine the depth gauge and a blonde woman is visible to the far left of the scene under the captain's extended arm.
Corrected entry: When Johann the engineer cracks during a depth charge barrage, the skipper hurriedly retrieves his pistol. After Johann is subdued, the weary skipper lays the weapon down unfired. It is a Walther P.38, but a postwar model, as revealed by the grips and alloy frame. Also, a lieutenant commander would probably have had a Walther PPK or Navy Mauser.
Corrected entry: The skipper of the WESER welcomes the U-boat's first officer and calls him Kapitänleutnant (Lt. Captain), although it must obvious to him that the man is no more than a Oberleutnant (First Lieutenant). An Oberleutnant shows two narrow golden rings on his sleeve, while a Kapitänleutnant shows one narrow between two wide rings. (02:16:35)
Corrected entry: In the underwater scene following the first depth charge attack the large calibre machine-gun behind the conning tower can't be seen. Was this a different boat or model?
Corrected entry: In order to make sure the cast looked the part and had the pale, pasty complexion that the real submariners would have had from being cooped up in the sub for such a long period, they were kept indoors for the shoot's duration.
Corrected entry: At the end of the movie, as the sub sinks, it disappears below the surface of the water, and we should see a large amount of bubbles as air is forced out the open hatch of the conning tower by the water flowing in. Even if the conning tower hatch was closed, there should be air bubbling out from somewhere as it is displaced by the water.