In Lough Swilly lies the SS Laurentic, a passenger boat which was carrying a fortune in gold to repay British War Debts. There were 475 people on board at the time, when the British vessel struck mines left by a German U-Boat on 25 January 1917. Only 121 survived, with 354 dying at sea. The ship had made an unscheduled stop at Buncrana and set off again when it was struck by the mines just off Lough Swilly. It only took around 20 minutes for the ship to go down. Of the £5 million worth of gold bullion that the ship was carrying, 99% was recovered by a British naval salvage team.
Popular amongst advanced scuba divers, the top of the wreck is at 36m and the seafloor is at 42m. It can be dived at any state of the tide. Lough Swilly is one of three glacial fjords in Ireland.