Special mark buoys

Used to indicate a special area or feature

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Marks used to indicate a special area or feature whose nature may be apparent from reference to a chart or other nautical publication. They are not generally intended to mark channels or obstructions where other marks are more suitable.

Their shape will not conflict with that of navigational marks. This means, for example, that a special buoy located on the port hand side of a channel may be cylindrical but will not be conical.

Special marks may be lettered or numbered, and may also include the use of a pictogram to indicate their purpose where appropriate.

Examples of uses of Special Marks.

  • Ocean Data Acquisition Systems (ODAS) marks
  • Traffic separation marks where use of conventional channel marking may cause confusion
  • Spoil Ground marks
  • Military exercise zone marks
  • Cable or pipeline marks
  • Recreation zone marks
  • Boundaries of anchorage areas
  • Structures such as offshore renewable energy installations
  • Aquaculture

Data Buoys are also classed as Special Marks.

Colour of special marks

They are coloured yellow.

Type one buoy with modular superstructure.JPG

Class 1 special mark buoy with modular superstructure being loaded onto our vessel THV Galatea in front of our Harwich HQ.

Type one buoy with stretched light weight alluminium superstructure LAS.JPG

Class 1 special mark buoy with stretched light weight aluminium superstructure (LAS)

Buoy services

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

Colour, shape and light

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Colour Yellow
Shape of buoy Optional, but not conflicting with lateral marks
Top-mark (if any)

Single yellow “X” shape

Light (when fitted)
Colour Yellow

Any, other than those reserved for cardinal, isolated danger and safe water marks


The use of pictograms is authorised, as defined by a competent authority

Emergency wreck buoys

Used as a temporary buoy to mark a wreck

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