The scene where the Engineer cracks up is really memorable.
It sure is.
I have fortunately never been in combat, but in reading accounts of men in combat, one of the things it seemed they were most fearful of (besides being maimed or killed) was being perceived by their fellows as cracking up. It was a form of weakness nobody wanted to see or undergo, and when it was seen in someone, other men were embarrassed by and for the guy who was going to pieces.
I do believe they fear it because I also believe it is contagious.
When I saw that scene in Das Boot, that was what I thought about. A large group of men, holding onto their sanity by the thinnest of threads after being depth charged like that, and having someone go over the edge.
I could understand why, in the movie, the Captain would consider shooting him.