Anonymous submarine sighed in the Black Sea according to a letter of the German naval attaché at Istanbul dated 2 December 1939

In his letter dated Istanbul, Turkey 2 December 1939 No. 491 g. reported the German naval attaché to the Oberkommando der Wehrmacht Abteilung Ausland that according to the press un anonymous submarine was sighted. In fact was it not a submarine but just a wreck. It was reported to prevent custody.

Source

Bundesarchiv. German Marineattaché for Turkey, Greece, Romania and Bulgaria 1939-1941. RM 12-II/459.