NavList:

David, I will give this a try based on translating numerous war diaries and meeting a number of U-boat veterans.  All the line officers on a U-boat  (Captain, First and Second Watch Officers) had a working knowledge of celestial navigation and occasionally practiced with the sextant.  Any Midshipmen assigned to the boat would have received instruction and would be expected to demonstrate their proficiency.  Like sending Morse with the signal lamp it was a basic skill for a professional officer but not something that he would necessarily be an expert in or practice every day.  The Navigator's training, experience and proficiency would usually greatly exceed the line officers who were primarily concerned with the safe and efficient operation of the boat as an instrument of war.  On most boats the First Watch Officer was also responsible for overseeing the torpedo armament and the Second Watch Officer was responsible for the Anti-aircraft guns and cannon as well as overseeing the Radiomen.  They were too busy to get directly involved in navigation, particularly during combat operations.  Navigation on a U-boat was a demanding full time job which had to be the responsibility of one person.  Although the navigator had his assistants (sometimes a Midshipman or an aspiring sailor from the seamanship branch) to help take sights and keep the DR plot going while he slept, you could not have multiple people making inputs.  On most boats the Navigator also served as the head of one of the three bridge watches and also served as the supply officer.  The relationship between the navigator and the Captain was close because accurate navigation was so important to the operation of the boat (maneuvering in coastal waters, taking position in a patrol line with other boats, meeting for supply, reporting a convoy or intercepting one reported by another boat).  The Captain had to trust in his navigator and worked closely together so it is understanding that they developed a close relationship.  The Captain and Navigator often stayed together through many patrols while other crewmembers came and went.  Having said that there was always a professional distance.  The Navigator was usually a senior Chief Petty Officer and not a member of the wardroom.    For a look at the personal photos of a U-boat navigator see http://uboatarchive.net/U-756.htm  Since you mention Das Boot, you can read the KTB of U-96 for the patrol on whcih Das Boot is loosely based here http://uboatarchive.net/KTB96-7.htm