There was a stage in the training of many U-boot captains called "Kommendantenchuler" (forgive me if that spelling is incorrect) - often translated into English as "Commander under training". In addition to theoretical instruction and work on "school boats" in home waters, this was an opportunity for officers being trained to work with experienced captains on actual combat patrols.
I don't know if it was typical for instruction in every phase of the War, but it was certainly common at many times.
Of course, most captains had been on many patrols as 1st or 2nd Watch Officers prior to being selected for Commander's training as well but the "Kommendantenchuler" training was designed to be even closer to the Captain's experiences and responsibilities. Many officers who later proved to be outstanding commanders served in "Kommendantenchuler" under Topp and Suhren.
There was a similar training program for LI's, as well.