Although the Polish guards are shown shooting prisoners as they try to escape from below decks after the torpedoing, historically they were carrying unloaded rifles and were not even issued with any ammunition. However they were issued bayonets for their rifles and therefore most of the many Italian prisoners killed by guards were bayoneted.
At the dry dock scene, the U-Boat officers walk by a ship with a bulbous bow, a feature that was not adapted by the German Navy until the 1950's.