HMS Royal Oak
HMS Royal Oak was a British battleship. It was built in 1916 and fought in the Battle of Jutland the same year. On 14 October 1939, soon after the start of World War II, it was sunk in Scapa Flow in Orkney, Scotland by the German submarine U-47. 835 people on the ship died when it sank, including the ship's admiral Sir Henry Blagrove. Many of the dead were boys younger than 16. The sinking affected people from both Germany and Britain: the commander of the German submarine, Günther Prien, was given a medal by Adolf Hitler, and the British quickly built sea walls to stop such a thing happening again.
Every year, Navy divers put a flag on the ship's stern.