there were more cases of u boat commanders helping the crews of enemy ships sunk during world war 2
it was at the commanders discresion how he assisted.
there are countless recounts of u boats directing survivors to the nearest coastline or even towing them on the surface.
sometimes food and medical tratment was given, obviously as u boats are relatively small inside there is not a lot of room for survivors/prisoners
so they made sure (where practicable) and not putting themselves or the boat in any danger.
this ended when the americans attacked a surfaced boat that was towing a string of lifeboats towards the shore,this practice stopped immediately after this incident with the majority of the boats, however some still ensured that the men in the water were able to reach a raft or some form of life boat, some boats leaving a rubber raft behind.

let us not forget that these were men who seved in the u boats and not unfeeling fanatical nazi machines as they are portrayed to be in americanised history and hollywood.

what about the bismark survivors they were left in the water until most of them had perished, there was no reason that they couldnt be picked up by the countless ships that were in the vacinity, u boat threat or not.

remember in the cruel sea where they depth charge the survivors?