There was no recorded wreck at this place so it had been reported for the appropriate authorities, including the Receiver on the Wreck (RoW). They were considered great boats. Throughout the war eight had been sunk, three surrendered and were at some point scrapped, and two were being regarded missing. https://charlieyvlyg.madmouseblog.com/14650732/the-smart-trick-of-u31-that-nobody-is-discussing