What is "danlayer"

A danlayer was a type of vessel assigned to minesweeping flotillas during and immediately after World War II. They were usually small trawlers, fitted for the purpose of laying dans. A dan is a marker buoy which consists of a long pole moored to the seabed and fitted to float vertically, usually with a coded flag at the top.

Dan laying was an important part of minesweeping, and boats were fitted specifically for this purpose. The task of a danlayer was to follow the minesweepers as they worked an area, and lay the dans which defined the area swept and made it obvious where the clear channels were. This would also help the minesweepers cover areas accurately without gaps and unnecessary overlaps. A danlayer worked with a minesweeper flotilla when large areas of sea were to be clear-swept.