At 17.05 hours on 3 March 1942 the unescorted and unarmed Mary (Master Severin Broadwick) was hit by two torpedoes from U-129 about 165 miles off the north coast of Brazil, while steaming on a nonevasive course at 10 knots. The first torpedo struck on the port side at the #3 hold. The explosion blew a column of water over the bridge, wrecked the radio shack and killed one crewman. The second struck about 8 seconds later at the #4 lower hold. Most of the eight officers and 26 crewmen had abandoned ship in two lifeboats, before the ship was hit by a coup de grâce at 17.17 hours on the port side at the #1 hold, causing the ship to sink about 15 minutes later. The U-boat surfaced and Clausen questioned the survivors in the boat of the master before leaving the area.
The survivors in the lifeboats were picked up after sailing 540 miles in six days by the American steam merchant Alcoa Scout about 38 miles northeast of Georgetown, British Guiana and taken to Port of Spain, Trinidad.

The master Severin Broadwick also lost his next ship to a U-boat, when the George Calvert was sunk by U-753 (von Mannstein) on 20 May 1942. He survived the sinking again, but lost another ship to a U-boat, when Thomas Ruffin was so badly damaged by U-510 (Neitzel) on 9 March 1943, that the ship was declared a total loss.