For years, German submarines U-19, U-20, and U-23 were a terrifying presence beneath the waves, preying on British and Russian shipping. Then, 60 years ago, they suddenly vanished to the bottom of the Black Sea.
The fate of "Hitler's lost fleet" was the talking point of a conference on international shipwrecks at Plymouth University at the weekend, when the Turkish marine engineer Selcuk Kolay described his painstaking search for the missing wrecks.
The search began along the Turkish coast near the town of Zonguldak in 1994, after the Turkish navy complained that it was having difficulty conducting minesweeping operations. Local people had known for years that the submarines were out there under the water somewhere, though the remarkable story of the U-boats is one of the lesser known episodes of the war.
The three submarines were originally part of a six-boat flotilla harassing Allied shipping around the North Sea. U-23 had patrolled the Spanish coast during the civil war, under the command of a young Sea Lieutenant, Otto Kretschmer, who was to become Germany's top U-boat ace. He was known as "Otto the Silent" for his mastery of silent running and his reluctance to make radio contact with Germany while he was at sea.