What does an isolated danger mark look like?
Black with one or more broad red bands, two black balls as a topmark, and a white Fl(2) light.
It's placed on, or moored above, a small danger such as a rock or wreck with navigable water all around it. You can pass either side, but give it a sensible berth: the danger is right underneath.
- Memory aid: two balls, two flashes.
- Shape is optional; usually a pillar or spar.
Source: IALA Maritime Buoyage System, isolated danger marks.
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