- Breakthrough Hit: For both Wolfgang Petersen and Jürgen Prochnow.
- Creator Backlash: The book's author apparently hated the movie for being a 're-glorification' of submarine warfare and too pro-German and pro-war (unlike the clearly anti-war novel it was based on) and for the cast's constant overacting. This has led to a Death of the Author reaction from many of the film's fans; when he claims that the movie "re-glorifies" the U-Boat Corps, the most common reactions are "How in the world is any of this supposed to be glorious?" - and "If the author considers this a glorification of WWII Era submarine warfare, how miserable must it have been in actuality?"
- Dawson Casting: Klaus Wennemann, who portrays the Chief Engineer, was forty one years old when the film was produced. The actual Chief Engineer of U-96, Hans Peter Dengel, was just over twenty five during his first patrol onboard the submarine.
- Enforced Method Acting:
- The actors were not allowed to expose themselves to sunlight a few months before shooting. Also, the scenes were more or less shot chronologically, so that their appearances would change realistically.
- Jan Fedder, who played the injured sailor, really was injured when a special effect went wrong.
- In the scene at La Rochelle harbor near the beginning, actor Otto Sander, playing a drunk Phillip Thomsen really was drunk. Originally another actor was slated to play that part, but he was fired before filming began...ironically enough, because he was too drunk all the time.
- The cast were required to run drills of the emergency dive sequence, to ensure they were able to convincingly carry out the tasks the real crews had to perform during an emergency dive.
- Prop Recycling:
- The original set of the U-96 was later reused as the World War I submarine U-20 for Lusitania: Murder on the Atlantic.
- Steven Spielberg borrowed their full scale, floating replica of a German U-Boat, for Raiders of the Lost Ark. This happened in the middle of filming, leading to a bit of a panic when the German crew woke up one morning and found the prop to be missing.
- Throw It In!: To simulate the storm in the Atlantic, a model of the tower was splashed with water from a large tank. Actor Jan Fedder lost his grip on the railing and was washed off the model, breaking a few ribs in the fall, one of the other actors instantly shouted "Man Overboard". At first Petersen didn't realize it was an accident but enthusiastically yelled "Good idea, Jan. We'll do that one more time!". Peterson still kept the scene and rewrote Jan Fedder's part in the film, so that his character spent a short portion of the movie in bed. The actor actually had to be brought back and forth from the hospital every day because of concussion. The painful expression on his face is real and not acted. (The scene which features him bedridden is available on the uncut edition.)
- What Could Have Been:
- Rutger Hauer was offered the role of the Captain, but he turned it down in favour of Blade Runner.
- When this was originally mooted as a German-US co-production, Robert Redford and Paul Newman were both considered to play the part of the captain.
- Several additional scenes were scripted based on the original novel, but in the end were never filmed due to budget and time constraints. In the original script, the U-Boat departs from St. Nazaire and docks at La Rochelle only at the end of the film due to heavy damage and an inability to reach its home port. The escape out of Gibraltar is also extended somewhat including the U-boat stopping a passenger liner and nearly sinking it, but at the last moment realizing the ship is of Spanish registry. The U-boat also encounters another submarine with an inexperienced crew at the entrance to La Rochelle harbor. The second submarine strikes a mine and the entire crew must be rescued. Finally, the character of Lieutenant Werner is much more heavily explored in the original script, including a love interest where Werner was seeing a French girl and by the end of the film suspected she was a member of the French resistance.
Trivia / Das Boot