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Buoyage – The signposts of the sea

Boating Knowledge

In 1977 the International Association of Lighthouse Authorities – IALA – adopted two systems of buoyage across the world. These are referred to as “Region A” and “Region B”. With the exception of the Americas and parts of Asia, the system used by the rest of the world is “Region A”. In England and Wales, buoyage is provided by Trinity House and conform to “Region A”. In Scotland and the Isle of Man the buoys are maintained by the Northern Lighthouse Board. Buoys can be distinguished by:

  • The colour of their light and flashing sequence
  • The colour and combination of colours on the buoy
  • The shape of the top mark

The marking system has been devised that a buoy may be identified if the light is not working or the top mark is missing.

Lateral Marks

Lateral marks can best be described as those buoys that tell you where you should and should not be! They mark the navigable part of the channel and are divided into Port and Starboard marks. Port marks are red in colour and shaped like a can, while starboard marks are green and conical in shape. In Europe, the position of each buoy is such that on exiting a harbour or channel the red marks or Port marks will be kept on your right hand side, while on entering a harbour or buoyed channel the green or Starboard mark will be kept to your right. A simple way of remembering the direction is “POSH” Port Out, Starboard Home.



The direction of buoyage is marked by an arrow on a chart


Port Lateral Mark

Port red bouy   lateral_port_night


Flashes red at night



Starboard Lateral Mark

Starboard green bouy




Flashes green at night



Cardinal Marks

Cardinal marks get their name from the cardinal points of the compass – North, South, East and West. They indicate where the safe water is and are used in conjunction with a compass. On seeing a North cardinal, the vessel should look to keep to the north, a south cardinal to the south and so on.

Cardinal marks are distinctive in that they are black and yellow in colour with two black cones. At night, a white light flashes in sequence and can either be quick (Q) or very quick (VQ)

North Cardinal – pass to the north

North CardinalNorth Cardinal



Continuous flashing. Q or VQ




East Cardinal – pass to the East

East CardinalEast Cardinal



3 flashes every 5 or 10 seconds. VQ or Q




South Cardinal – pass to the South

South CardinalSouth Cardinal



6 plus 1 long every 10 or 15 seconds. VQ or Q




West Cardinal – pass to the west

West CardinalWest Cardinal



9 flashes every 10 or 15 seconds. VQ or Q




Isolated Danger Mark

The isolated danger mark is used when there is clear water all round the object of concern but the danger lurks directly below the buoy or pile. The day mark is identified as two black balls and the overall colour is black and red. An easy way to remember the mark is that Dennis the Menace’s T-shirt is black and red!

Isolated Danger Markisolated_danger_night



Two white flashes




The Fairway or Safe Water Mark

This mark usually denotes the start of a buoyed channel, while there is safe water all round, be on the look out for the start of a buoyed channel with port and starboard lateral marks.




White occulting, isophase,LFl 10s
or Morse “A”




Special Mark

While of no navigational significance, special marks are used widely to denote such things as bathing areas, marking outfall pipes and race turning marks. They are solid yellow in colour, although orange marks may be also found, particularly in the Solent.




Flashing yellow




Emergency Wreck Buoy

The Emergency Wreck Buoy is a new addition to the buoyage system and is used, as it’s name implies, to mark the site of a wreck. It is positioned as close to the wreck as possible and will remain in position until:

  • the wreck is well known and promulgated in nautical publications
  • the wreck has been surveyed and exact details such as position and least depth above the wreck are known
  • a permanent marking has been positioned

The main characteristics of the bouy are:

  • coloured in equal number and dimensions of blue and yellow vertical stripes
  • fitted with an alternating blue and yellow light with a nominal range of 4 nautical miles. The blue and yellow flashes of one second will alternate at half second intervals.
  • the lights will be synchronised where two are more buoys are in position
  • the top mark is an upright yellow cross.



Alternating blue and yellow flashing lights


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