Three all-round green lights in a triangle, above a power-driven vessel's lights. What is she doing?
Lights seen at night, from top to bottom: white (centre), green (centre), green (left), green (right), green (left), red (right).
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Mine clearance: stay at least 1,000 metres away. Three green lights (or three balls by day) mean mine clearance. It is dangerous to come within 1,000 metres of her.
