There was no recorded wreck at this locale so it had been reported into the applicable authorities, including the Receiver on the Wreck (RoW). They were being regarded great boats. Through the war 8 were being sunk, 3 surrendered and were being finally scrapped, and two have been considered lacking. https://u3122119.shotblogs.com/not-known-factual-statements-about-u31-48084525