Scuttled U-boats - Type XXI
U-3539 - U-3542 (4 U-boats) were scuttled at Schichau, these boats were about 80% complete at the time.
U-2505, U-3004 and U-3506 were not really scuttled along with the other boats but rather trapped inside the Elbe II fitting-out bunker in Hamburg. There they stayed undiscovered until 1985. For further information please check out the U-3004 page.