At 12.50 hours on 19 March 1944 the Seakay (Master Alfred Kristian Jorgensen) in station #51 of convoy CU-17 was hit by one FAT torpedo from U-311 about 375 miles west of Fastnet, just when convoy made an emergency turn to port. The torpedo struck the starboard bow at the after bulkhead of the forward dry cargo hold and set the kerosene, the deck cargo and the forward pump room on fire. The flames shot 25 feet above the deck and the crew immediately tried to extinguish the fire, but the ship sank rapidly and the ten officers, 46 crewmen, 28 armed guards (the ship was armed with one 5in, one 3in and eight 20mm guns) and one passenger (US Army security officer) abandoned ship five minutes after the hit in four lifeboats and a raft. One boat overturned during the launch and caused the loss of one armed guard.

The survivors were picked up by USS Reeves (DE 156) and landed at Londonderry on 21 March. The tanker capsized within 18 minutes, but remained afloat with the stern out of the water at a 45° angle and was scuttled by escort vessels with 45 shells and three depth charges.