A white light flashes in groups of two, as shown. What kind of mark is it?
A timeline of a white light at night, 15 seconds long. Two short flashes close together, then about 3 seconds of darkness, repeating every 5 seconds.
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An isolated danger mark. White group flashing two, written Fl(2), is the isolated danger mark: think of the two black balls on top of it. It sits on a small danger with safe water all round, so do not pass too close.
