At 22.06 hours on 6 December 1942 the unescorted Serooskerk (Master Doekele de Boer), dispersed from convoy ON-149 the day before, was hit on starboard side by one of two G7a torpedoes from U-155 while steaming on a zigzag course in a moderate sea about 400 miles west-northwest of the Azores. The U-boat had chased the ship since 19.50 hours and observed how she stopped after being hit, but did not sink. One G7a torpedo fired as coup de grâce at 23.17 hours struck on port side underneath the aft mast, only causing the ship to settle slightly by the stern. However, the Serooskerk sank within two minutes after being hit on port side amidships by another G7a torpedo fired as coup de grâce at 23.55 hours. The Germans assumed that the first torpedo had hit at the waterline as surface runner, probably wounding and killing many of the crewmen and destroying the lifeboats because despite the long time between the attacks no survivors were seen to abandon ship. The master, 89 crew members, nine gunners (the ship was armed with one 4in, one 37mm, four 20mm and two machine guns) and nine passengers were lost.