The German cargo ship S/S Ingrid Horn was en route from Luleå to Germany with a cargo of iron ore on the quiet night of July 31st, 1917. To save on costly kerosene, her lanterns had not been fully lit. It would prove fatal.
The Swedish cargo ship S/S Bergvik was headed for Dalarö when the pilot saw a white light. At first he assumed it to be light of a ship at anchor, but as the Bergvik got closer the pilot also saw a faint red light. It then became clear that these were the lights of a ship underway and that there was now a serious risk of collision. The captain ordered full astern, but it was too late. The Bergvik's bow penetrated 3 meters into the side of Ingrid Horn and she began sinking fast.
The Ingrid Horn was built in 1901, a huge steamship over 90 meters long. The accident would kill 19 of the crew. Today the wreck lies in the channel at a depth of 30-40 meters. The two meter wide hole from the collision can still be seen today on the port side.