Buoyage (IALA A)

A note about Lateral marks:

IALA = International Association of Lighthouse Authorities 

IALA A = UK & rest of the world excluding areas noted in IALA B

IALA B = USA, Japan, North & South Korea and the Phillipines

The system consists of lateral, cardinal and other buoys, such as isolated danger and safe water marks. Buoys can be distinguished from each other by

  • the colour of their light and flashing sequence
  • the colour and combination of colours on the buoy
  • the shape of the topmark

This marking scheme is designed to enable mariners to identify a buoy if the light is extinguished and /or the topmark is missing.

Lateral buoys mark well defined channels and indicate port and starboard hand sides of the route to be followed, for port hand marks the buoy and light are coloured red, for starboard marks these are green.

Cardinal buoys are used in conjunction with a compass to indicate where a mariner may find the best navigable waters. They are coloured yellow and black and have white flashing lights.

cardinal marks:

What do they tell us ? Indicating safe water

North Cardinal

Light sequence: White light either Quick or Very quick flashes continuously.

East Cardinal

Light sequence: White light either Quick or Very quick flashes x 3.

South Cardinal

Light sequence: White light either Quick or Very Quick flashes x 6 + 1 long

West Cardinal

Light sequence: White light either Quick or Very quick flashes x 9. 

lateral marks:

What do they tell us? Mark the edge of channels

Port Lateral Mark

Light Sequence: Flashes Red (various sequences (other than 2+1), dependant on area - refer to chart)

Starboard Lateral Mark

Light Sequence: Flashes green (various sequences, dependant on area - refer to chart)

Preferred Channel to Port

Light Sequence:

Red Flashes (2+1)

Preferred Channel to Starboard. 

Light Sequence:

Green Flashes (2+1)


other marker buoys:

Isolated Danger Mark

Light sequence: Flashes white x 2

Temporary Wreck Mark

Light sequence: Alternating blue and yellow 1 second flashes with an interval of 0.5 seconds. 

Safe Water Mark

Light sequence: White (various sequences - check chart for details)

Special Mark

Light sequence (if it has one): Yellow flashing (various sequences depending on area - refer to a chart

Contact us:


Tel: +44 (0) 1202 024111

We DO want to talk to you, but if possible, pls email / send a WhatApp message for the quickest response as we are generally busy teaching... 

Our Locations:

Powerboat & Jetski: Port of Poole Marina

Powerboat: Lake Yard Marina
Shorebased: Romany Works, Poole

Post Course eFeedback Form - Click Here

Follow us on Facebook:

Our Companies:

RYA Training Centre

Marine Education

'The Superyacht Jetski Specialists'

Superyacht PWC

Superyacht Marine Store

Marine Store EU