An Isolated Danger mark is placed on, or moored on or above, an isolated danger which has navigable water all around it.
Because the extent of the danger and the safe passing distance cannot be specified for all circumstances in which this mark may be used, the mariner must consult charts and nautical publications for guidance.
Typically used to mark hazards such as an underwater shoal or rock.
Colour of isolated danger marks
They are coloured black and red.
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Colour, shape and light
ISOLATED DANGER MARK |
DESCRIPTION |
| Colour |
Black with one or more broad horizontal red bands |
| Shape of buoy |
Optional, but not conflicting with lateral marks; pillar or spar preferred |
| Top-mark * |
Two black spheres, one above the other |
| Light (when fitted) | |
| Colour | White |
| Rhythm |
Group flashing (2) |
* The double sphere topmark is a very important feature of every Isolated Danger mark by day, and should be used wherever practicable and be as large as possible with a clear separation between the spheres.