Corvette HMCS La Malbaie arrived Halifax from builder Sorel, Province of Quebec.

At 0358, the unescorted Koenjit was torpedoed by U-156 about 300 miles NNE of Barbados. One torpedo struck aft in the engine room and she began to sink over the stern. All crewmembers abandoned ship in two lifeboats, except the master and the first mate Folmer, who stayed aboard and searched for possible crewmembers still on board. They later had to jump overboard as the ship sank and swam to the boats. The U-boat surfaced and Hartenstein asked for the name, nationality and destination of the ship. The answers he got from the crew were so short and so vague that he was not able establish the identity. He then gave the position to the survivors and left after the ship disappeared under the surface. The motorboat Letitia Porter carried on deck went down with the Koenjit.

At 0234, the unescorted Esso Houston was hit by one torpedo from U-162 about 150 miles east of Barbados, just after lookouts spotted the U-boat crossing the bow of the tanker, which immediately put the wheel hard right. The torpedo struck on the port side instead of the starboard side, about 25 feet aft of the bridge at the #6 hatch and blew oil over the after part of the ship. The engines were stopped and the damage was examined. It was realized that the back was broken and the eight officers, 30 men and four armed guards (the ship was armed with one 4in gun) abandoned ship in three lifeboats and one raft. 20 minutes later a second torpedo struck amidships, destroying the ship. U-162 surfaced near the lifeboats, questioned the crew, offered assistance and left. The U-boat returned to let the master know that one of the lifeboats was in sinking condition near the stern of the tanker. 18 survivors in one boat were picked up by the Norwegian motor tanker Havprins 40 hours later, were transferred to the Latvian SS Everagra the next day and landed at St Thomas, Virgin Islands on 18 May. 23 survivors on another boat made landfall five days after the attack on St Vincent Island. One armed guard died from injuries.

At 1230, the unescorted and unarmed Gulfpenn was steaming five miles ahead of the Gulfprince, when the other tanker was attacked by U-507. The Gulfpenn immediately left the scene on full speed and later steered zigzagging course in irregular patterns at 12.5 knots. At 2138 on the same day, U-506 fired one torpedo, which struck the Gulfpenn aft in the engine room on the starboard side, killing all men on watch below and immediately stopping the engines. 26 men from the eight officers and 30 crewmen abandoned ship in two lifeboats. One crewman later died of wounds. One officer and 11 crewmen died in the explosion or went down with the tanker; two of these died trying to retrieve personal papers. The ship made a half-circle and then plunged stern first within five minutes about 30 miles off the entrance to the Mississippi River. Three hours later, the survivors were picked up by the Hondurian Telde, which had been directed to them by a USCG aircraft and taken to Pilottown, Louisiana and thence to New Orleans. A lookout on the Gulfprince spotted the periscope one mile astern and the tanker proceeded on a zigzagging course at 10 knots. The first and second torpedo fired by U-507 at 12.38 and 13.39 hours were skilfully evaded, the first passing ahead and the second passing astern. But the third torpedo fired at 13.41 hours struck the tanker a glancing blow on the starboard side aft and abreast of the #8 main cargo tank. After glancing off, it jumped into the air about three feet and then submerged again. The collision sprung hull plates and four feet of oil leaked from the tank. The tanker continued under full steam on a zigzag course to escape. None of the eight officers and 34 crewmen on board was injured. She arrived New Orleans and went into dry dock for repairs after discharging her cargo and returned to service on 15 Jun 1942. The Gulfpince had been en route from Port Arthur, Texas to New York with a cargo of 71.000 bbls of crude oil.