Isolated danger mark buoys

Marking small, isolated dangers with navigable water around the buoy

isolated danger mark buoy 2.png

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.

Buoy services

Buoys are available for hire, contact us for more information.

Colour, shape and light

isolated danger mark.png




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

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.

Safe water mark buoys

Indicate the presence of safe, navigable water all around the buoy

Get our regular newsletter