HMS Royal Oak was a Royal Navy battleship, and the last to be built at the Devonport dockyards in Plymouth. She was launched in 1914 and took part in the Battle of Jutland during World War I.
On October 14th, 1939, she was lying at anchor in Scapa Flow when the German U-Boat U-47 snuck past anti-submarine defenses and torpedoed her. She sank within 10 minutes of being struck by the second salvo of torpedoes from U-47, with the loss of 833 of her crew.
HMS Royal Oak was one of the first major losses for the Royal Navy during World War II, just six weeks into the war. Now she lies upside-down in 30m of water in Scapa Flow, and is designated a war grave, and a new battle ensign is raised over her each year in remembrance of those who died.