At 04.12 hours on 13 June 1942 the unescorted Sixaola (Master William H. Fagan) was hit on the starboard side by two torpedoes from U-159, while steaming on a righthand zigzag pattern at 12.5 knots about 50 miles off Bocas del Toro, Panama. The first torpedo struck in the bow and the second in the center of #2 hold. The most of the eight officers, 79 crewmen, six armed guards (the ship was armed with one 3in and two .50cal guns) and 108 passengers on board abandoned ship in five lifeboats and six rafts two minutes after the hits and stopping the engines. 29 crewmen died in the explosions, most of them lay sleeping in the quarters of the crew in the bow. Just after the master and chief officer left the ship, she was hit on the port side amidships by a coup de grâce at 04.31 hours and sank by the stern about 06.15 hours. The Germans questioned the survivors, offered medical aid, gave exact course and distance to the nearest land and two packages of German cigarettes and then left the area.

32 survivors in one boat were picked up by the American steam merchant Carolinian and later transferred to the American gunboat USS Niagara (PG 52), which also picked up 75 survivors in two other boats that had been spotted by aircraft and landed them all in Cristobal. 23 survivors in another boat were rescued by the US Army tug Shasta, after their boat landed on Bocas del Toro on 16 June. The remaining 42 survivors made landfall in their lifeboat in the delta of Coloveboran River after four days and were brought to Cristobal by the American submarine chaser USS PC-460.