In 1939, a Nazi Submarine Slipped into One of Britain's Biggest Bases and Sunk a Battleship

HMS Royal Oak at Scapa Flow. Did not read linked story due to site being in maintenance mode.
It is interesting that the British had just reopened the base and was just starting the process of surveying and repairing or replacing the deteriorated WWI defenses.

Oh, the stories I’d like to tell you.

Love these tidbits of history ! Thanks for sharing !