There was no recorded wreck at this place so it had been noted for the relevant authorities, including the Receiver of your Wreck (RoW). They were being considered superb boats. Through the war 8 were being sunk, 3 surrendered and ended up inevitably scrapped, and two had been regarded lacking. https://marioaaufs.snack-blog.com/34111206/the-smart-trick-of-u31-that-nobody-is-discussing