I was interested to read in the news of late that the wreck one of the very few Type XXI U-Boats to see active service was recently found using multibeam SONAR. These were really revolutionary vessels - arguably the first real 'submarine' with theoretically unlimited underwater performance - everything up until then had just been a 'submersible'. The Allies plundered this tech mercilessly in the post war - early cold war years and fed into design of the diesel SSKs and early nuclear SSBNs and SSNs.
It is quite a dramatic wreck too, telling a lot about the last moments of the ship. U-3523 is buried from the bow up to the midships in the mud near the Skaggerak (Denmark) at almost a 45degree angle, it must have hit the seabed with some force. Uncontrolled flooding, bowplanes stuck - who knows what happened following the aerial attack to have made U-3523 plow into the seabed at that angle, 120m below the surface but this is one of the boats that had long been rumoured to have slipped off to South America with Nazi gold and/or war criminals and that story can also be laid to rest now.