In the IALA A system, used in New Zealand, Europe and Australia, keep red port-hand marks on your port side and green starboard-hand marks on your starboard side when entering harbour. Leaving harbour, it is the other way round.
Red and green buoys and beacons are lateral marks. They show the two sides of a channel, and they are always read in relation to the direction of buoyage, which is the direction of travel going into harbour, up a river or estuary, or towards the head of a bay.
In the IALA A system:
- Port-hand marks are red. Buoys are can-shaped (a flat-topped cylinder), and a topmark, if fitted, is a red can. A light, if fitted, is red.
- Starboard-hand marks are green. Buoys are cone-shaped, and a topmark, if fitted, is a green cone pointing up. A light, if fitted, is green.
Going in with the direction of buoyage, keep the red marks on your port (left) side and the green marks on your starboard (right) side. Coming out, reverse it: red on your starboard side, green on your port side.
Where it is not obvious which way is "in", for example along a coast or in a channel between two islands, the chart shows the direction of buoyage with a special arrow symbol. Check it before you set off.
The shape matters as well as the colour. In poor light, or against the sun, colour is hard to see, but a can or cone silhouette is still clear. At night, the light's colour tells you which side it marks, and the pattern of flashes, printed beside it on the chart, tells you which mark it is.
Lateral marks show the edge of the channel, not a line to steer along. The water just outside a mark may be very shallow, so do not cut close to the wrong side of one. Also remember that in a channel shared with ships, keeping to the starboard side of the channel, or just outside it in safe water, keeps you clear of larger traffic.
In the Americas, Japan, Korea and the Philippines, which use IALA B, the colours are reversed.
More in the book: Chapter 14, Buoys, charts and tides