At 08.54 hours on 14 June 1942, U-172 fired one G7a stern torpedo at the unescorted Lebore (Master John William Jimmyer), which proceeded on a nonevasive course at 10.4 knots about 200 miles north of Cristobal. The U-boat had already fired two spreads of two torpedoes at 04.03 and 07.43 hours at the ship, but the first was not launched due to malfunctions and the second missed.
A lookout on Lebore spotted the wake 400 feet from the ship, but the helmsman had no time to avoid the torpedo, which struck on the starboard side at the #6 hatch. The explosion caused a hole in the #3 wing tank and jammed the after 4in gun (the ship was also armed with two .50cal and two .30cal guns). The tank rapidly filled with water and caused the ship to list 45° to starboard. At 09.18 hours, the ship was hit in the engine room by a coup de grâce, then shelled and eventually capsized after being hit by another torpedo at 10.39 hours. The wreck finally sank after being hit by 12 rounds from the deck gun at 12.35 hours.

The seven officers, 32 crewmen, six armed guards and 49 survivors from the Crijnssen, which had been picked up on 11 June after their ship had been sunk by U-504 (Poske) that day, abandoned ship in three lifeboats and four rafts. The first assistant engineer failed to leave the ship and drowned. 40 survivors were picked up by USS Tattnall (DD 125) after boats and rafts had been spotted by an aircraft on 16 June. Another 25 survivors were picked up from a boat by USS Erie (PG 50), which also rescued 28 survivors from St. Andrews Island, after they landed there in a lifeboat about 18 hours after the attack. All survivors were landed at Cristobal on 17 June.