At 13.21 hours on 20 May 1942, U-155 fired a spread of two stern torpedoes at two tankers in convoy OT-1 and hit the Sylvan Arrow (Master Arthur J. Beck) with one of them. The explosion blew oil all over the ship, buckled the main deck and set the midship section in flames. Some of the 38 crew members managed to launch two lifeboats and took off the remaining men from the bow where they had been trapped by the fire. The six armed guards manned the gun, but were later forced to jump overboard and one man drowned. All survivors were picked up by USS Barney (DD 149) and taken to Port of Spain, Trinidad. While 26 crew members were repatriated to New Orleans aboard the Robert E. Lee, the master and 11 crew members were engaged in a salvage attempt of their ship. They arrived at the wreck of Sylvan Arrow after three days and on 26 May she was taken in tow by a tug, but began to break up and finally sank on 28 May in 12°50N/67°32W. The burning and floating tanker had been spotted by U-155 at 15.00 hours on 21 May, but escorts and aircraft prevented a coup de grâce.

The master and 11 crew members were taken to Curaçao and boarded the Crijnssen, which was sunk by U-504 on 11 June. The master and six men were in a lifeboat that landed on the Yucatan coast and were later flown from Chetumal to Brownsville, Texas. 5 men were picked up the same day by the Lebore, which was herself sunk by U-172 (Emmermann) on 14 June. They were in a lifeboat for three days and picked up by USS Tattnall (DD 125) and landed at Cristobal.