Minesweeper

A vessel engaged in mine clearance operations shall in addition to the lights prescribed for a power-driven vessel, or to the lights or shape prescribed for a vessel at anchor, exhibit three all-round green lights or three balls. One of these lights or shapes shall be exhibited near the mast head and one at each end of the fore yard. These lights or shapes indicate that it is dangerous for another vessel to approach within 1000 metres of the mine clearance vessel.

Minesweeper, shorter than 50 m
Ahead, day signs (3 black spheres)	Ahead	Astern