In the book, he's less overtly laughable. I agree, during the course of the movie he becomes less spit-and-polish (probably because it was no longer possible to keep it up) and more sympathetic, especially when he asks the captain whether there's any chance they will be able to surface. "Gute Frage!" is the response ("Good kvestion!" said Jürgen Prochnow in the dubbed version.) I believe the real-life IWO was a rather inept young man who left the crew after they got back to port. In the novel, he does something which would have been highly at odds with the rules of seamanship except for an equipment failure. Io knows lots more about him than I do.