The crew inadvertently receives an uncoded voice transmission from a German supply ship indicating its destination. In fact, German supply ships were sent to meet U-boats at prearranged meeting locations by German headquarters back in Europe using coded messages. Therefore, the crew should never have understood the transmission. Since this movie was filmed during the war, these facts were likely unknown at the time.
The court martial at the beginning of the movie is about an incident on the USS Bayonne. As reference is made to the "forward turret" and the name is that of a city, the referenced ship would have to be a cruiser. However, no cruiser or any other type of ship in the U.S. Navy was named Bayonne before the war. In 1943, during World War II, the USS Bayonne (PG-129 / PF-21) was constructed. It was originally classified as a gunboat (PG), but this was later changed to a frigate (PF).
The radio signal about the German supply ship's position is inaccurate for a number of reasons. 1) Voice radio was used for only very short range transmissions. Morse code was used for all long range transmissions. 2) It was actually quite easy to hear most enemy radio transmissions. Decoding them was the difficult part. 3) "Garble" was used for some land based voice communications, but not with radio. Messages were coded before transmission and the encoded message was sent. Despite all this, the de-garbled radio code was a common plot device in U.S. war movies of World War II.