von Zelda

If I recall correctly from my reading, gun crews were trained military personel not merchant sailors.

Now as far as treatment (and I'm assuming you mean after their ship was sunk and they were in life boats or on rafts) survivors were probably treated fairly equally. Early in the war U-boat captains would hand out medical supplies, give food and directions to land, etc. As the war progressed, this became impossible because the safety of the u-boat was their priority.

Also, there was no room on a u-boat to take on survivors no matter what their classification might be; this made it necessary to leave survivors stranded at sea. Most seamen on both sides were very respectful of other shipwrecked sailors.

To my knowledge, there was only one documented case where a u-boat captain gave orders to sink all lifeboats and rafts so as not to leave a trace of a sinking by u-boat. This of course killed many of the survivors. Three lived to be rescued and tell of their ordeal. The u-boat captain as well as several officers having been capture by the British, were identitified, tried and convicted after the war.

There was another famous situation where a u-boat sank a ship named the Laconia. After which the u-boat captain determined the ship to have had Italian prisoners, Polish guards, British service personel as well as a few women and children on board. The u-boat captain radioed BdU and immediately began a rescue mission. Two other u-boats as well as a few Italian ships were directed to help. In the process the surfaced u-boat with a makeshift red cross flag laying on the deck was bombed by a US bomber. Ultimately a large number of survivors were rescued. Then Donetz issued the order that u-boats were no longer allowed to rescue survivors.

I hope this answers your question.