At 06.16 hours on 8 July 1942 the unescorted J.A. Moffett, Jr. (Master Patrick Sarsfield Mahony) was attacked by U-571 with a spread of two torpedoes 3 miles southwest of Tennessee Reef, Florida Keys. One torpedo struck one the port side at the #1 tank. The master tried to beach the tanker with a hard turn to starboard, but the engines were secured and the ship began to lose way. The most of the eight officers and 29 crewmen abandoned ship in two lifeboats and three rafts. The six armed guards manned the 4in and two .30cal guns to defend the ship, but a second torpedo struck after 15 minutes at the #8 tank on the port side. The disabled ship drifted in a semicircle until going aground on the Reef, at this point the gun crew abandoned the ship. As the lifeboat was launched, the arm of the master got caught in the falls and was amputated. He died of a loss of blood.

30 minutes after the first attack, the U-boat surfaced and began shelling the ship for five minutes, setting the midships house afire. The survivors were picked up by the US Coast Guard auxiliary crafts Mary Jean and Southbound within three hours and were landed at Craig, Florida. USCGC Nike (WPC 112) saved another man and brought him to Craig.

In October 1942 a salvage crew of Merritt, Chapman & Scott pulled the tanker of the reef and towed her to Key West, where she was declared a total loss. She was later towed to Galveston and scrapped in January 1943.