Regarding Vigil: there were a lot of “mistakes” from the view of the technical side.
Some statements were totally wrong, regarding the functionality of a submarine,
There are none in “Das Boot”
The author Lothar Buchheim (RIP) was a “Kriegsberichterstatter”
( war correspondent ) )
and the movie is really very close to the book.
(Buchheim checked the script)
Some scenes from the novel were not realized in the movie :
They stopped a huge passenger liner.
The 1WO found it in the “ship list” as an US-american ship. (troop ship)
The Commander ordered a boat to come to the submarine.
This didn’t come in time so they lanced a torpedo.
The torpedo failed.
Then the boat came and the captain brought the ship’s papers and it got clear the steamer was a Spanish one.
(5000 passengers to Buenos Aires)
The 1WO had not checked the appendix of the list were the ship was listed.
The steamer was sold to a Spanish company.
Now the ship’s name was “Reina Vittoria”.
Of course the names of the commanders etc in the novel (movie) are all fictive ones.
But there are great similarities to existing ones and their true stories.