At 03.31 hours on 24 June 1941, U-203 fired a spread of two torpedoes at a ship of 15.000 grt in convoy HX-133 during a surface attack by night, but the first did not detonate and the second missed the intended target and struck another ship in convoy. Two minutes later, a second spread of two torpedoes was fired and one detonation was heard, but no observations could be made because the U-boat had to crash dive. The only ship hit during the attack was the Soløy.

The Soløy (Master Arne H. Sørensen) was struck on the port side in the after part of #4 hold and received a leak in the tunnel. It was not possible for the first engineer to close the tunnel door, so the ship started to sink and was gone after 15 minutes. While the crew successfully launched the port lifeboat, the other boat on starboard had to be cut loose because a seaman got his hand jammed during the lowering. The boat broke apart after the fall into the sea and its occupants were thrown into the water. However, all men survived and were later picked up by Traveller and landed at Liverpool on 3 July.