Isolated Danger Mark

An aid to navigation placed on or moored above an isolated danger with navigable water all around it.

Under the IALA Maritime Buoyage System it is coloured black with one or more broad red horizontal bands and carries two black spheres as its topmark. Its light, when fitted, is white and shows a group of two flashes, matching the two-sphere topmark.

The mark identifies the danger’s position but does not state the clearance on every side or make close passage safe for a particular vessel. The chart, depth, scale, positioning accuracy and local conditions must be used to determine a safe route.

• Colour: Black with one or more red horizontal bands.
• Topmark: Two black spheres, one above the other, at the top of the mark.
• Light (if equipped): Flashes white, usually in a group of two flashes (to make it distinct from other marks).