On 21 November 1916 the "Britannic" hit a naval mine in the Kea Channel, off the Greek island of Kea. The mines had been put there by the German submarine U-73. A huge explosion tore a hole in the side of the ship which sunk one hour later. The ship which was carrying 1,125 people, and nearly all were saved. Two lifeboats were struck by the ship's propellers and 30 people were killed.