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.
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).
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.