SM U-86 was a Type U 81 style submarine manufactured in the Germaniawerft, Kiel shipyard for the German Empire during World War I. On 27 June 1918, under the command of Lieutenant Helmut Patzig, U-86 sank the Canadian hospital ship HMHS Llandovery Castle off the coast of Ireland in violation of international law. When the crew took to the lifeboats, U-86 surfaced, ran down all the lifeboats except one, and shot at the people in the water. Only the 24 people in the remaining lifeboat survived. They were rescued shortly afterwards and testified as to what had happened. The 234 others on board the Llandovery Castle were lost, including fourteen nursing sisters.