At 08.29 hours on 7 July 1943, U-185 attacked convoy BT-18 about 125 miles east of Fortaleza, Brazil for the second time and reported hits on a tanker and an ammunition ship that were sinking slowly. The ships hit were S.B. Hunt and Thomas Sinnickson.

The Thomas Sinnickson (Master Joseph Linder) had been in station #22, but took over #21 after the James Robertson had been torpedoed and was herself hit on the starboard side by two torpedoes. The first struck at the #1 hold and the second at #2 hold in one of the fuel bunkers, which blew up vaporized oil that was ignited and sent flames hundreds of feet into the air. The eight officers, 35 crewmen and 27 armed guards (the ship was armed with one 4in, one 3in and eight 20mm guns) remained on board and tried to save the ship, also because the explosion had blown three rafts overboard, one raft onto the stern gun platform and filled the starboard lifeboats with water and oil. One armed guard was killed by the explosions. The master tried to reach the coast in a distance of 90 miles by proceeding over the stern, but the pumps could not prevent the complete flooding of the bow compartments and the ship settled gradually by the head until the propeller was out of the water. About 13 hours after the attack, 18 men transferred to USS Surprise (PG 63), which radioed for a salvage tug that did not arrive as planned at 11.00 hours the next day. After a crack appeared in the bulkhead between the engine room and #3 hold, the officers came to the conclusion that the ship is lost and at daylight on 8 July all hands abandoned ship and were picked up by the corvette, which scuttled the wreck by gunfire at 14.30 hours and landed the survivors at Recife on 11 July.