IALA Buoyage System
The International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA) buoyage system provides a worldwide standard for maritime marks. Understanding these marks is essential for safe coastal and inshore navigation.
Region A vs Region B
Region A
Europe, Africa, Asia (most of), Australia, New Zealand, and most of the rest of the world. In Region A, red marks are on the port (left) side and green on the starboard (right) side when entering a harbour or sailing with the flood tide.
Region B
The Americas, Japan, South Korea, and the Philippines. In Region B, the lateral mark colours are reversed: green is on the port side and red on the starboard side. The American mnemonic "red right returning" applies — red marks are kept to starboard when returning to port.
Note: Only lateral marks differ between regions. Cardinal marks, isolated danger marks, safe water marks, and special marks are the same worldwide.
Lateral Marks (Region A)
Lateral marks define the edges of a navigable channel. The "direction of buoyage" is the direction you are sailing when entering a harbour from seaward (or travelling with the main flood tide direction).
Port (left when entering harbour)
Starboard (right when entering harbour)
Preferred Channel Marks
Where a channel divides, modified lateral marks indicate the preferred (main) channel:
- Preferred channel to starboard: Red with one green horizontal band (treat as a port mark — keep it to your left)
- Preferred channel to port: Green with one red horizontal band (treat as a starboard mark — keep it to your right)
Cardinal Marks
Cardinal marks indicate the direction of the safest water relative to the mark. They are named after the compass quadrant in which you should pass. The colour scheme is always black and yellow — the position of the black and yellow bands corresponds to the topmark direction.
North Cardinal
Pass to the north of this mark — danger is to the south.
South Cardinal
Pass to the south of this mark — danger is to the north.
East Cardinal
Pass to the east of this mark — danger is to the west.
West Cardinal
Pass to the west of this mark — danger is to the east.
Light pattern mnemonic:Think of a clock face. North = 12 o'clock = continuous. East = 3 o'clock = 3 flashes. South = 6 o'clock = 6 flashes + long flash. West = 9 o'clock = 9 flashes.
Other Marks
Isolated Danger
Marks a small, isolated danger with navigable water all around. You can pass on either side but not too close.
Safe Water
Indicates navigable water all around — used as mid-channel, fairway, or landfall marks. Approach from any direction.
Special Mark
Marks areas of special significance — cable zones, military exercise areas, water-skiing zones, outfall pipes, ODAS buoys. Not primarily for navigation.
Emergency Wreck Marking Buoy
Marks a newly discovered wreck until a permanent mark can be established. Keep well clear.
Exam tip: Cardinal mark questions are very common in Day Skipper and Yachtmaster exams. Remember the clock-face mnemonic for light patterns and the topmark rule: the points of the cones always point toward the black band(s).