sweeping for moored buoyant mines, but the Royal Navy resumed minesweeping operations the following spring, continuing to clear sunken mines from fishing grounds, and maintaining a destroyer patrol to track down mines that had broken free of their moorings and gone adrift. Losses of civilian ships to North Sea mines continued; the origin of the mine in these cases was often difficult to determine. In 1919, twenty crewmen drowned when the Swedish steamship Hollander sank, minutes after striking a mine in October; and the steamer Kerwood struck a mine and sank on 1 December. See also Otranto Barrage Notes Bibliography Conflicts in 1918 North Sea operations of World War I Naval mines