IALA Buoyage (Region A)

Nearly every coastal country uses one of two buoyage systems agreed by IALA, the body that coordinates marine aids to navigation. Europe, Africa, Australia and most of Asia use IALA Region A — everything in this course. (The Americas, Japan, South Korea and the Philippines swap the lateral colours in Region B.) Lateral marks show which side of a channel to pass. Entering harbour, red can-shaped marks are left to port and green cone-shaped marks are left to starboard — shape and colour saying the same thing twice, so the silhouette alone is enough at dawn. The lights match: red for port-hand, green for starboard-hand, in any rhythm, because a rhythm's only job is to tell one buoy from its neighbour.

Lateral mark

A buoy or beacon marking the side of a channel. In Region A: red can to port, green cone to starboard, when travelling with the direction of buoyage.

Direction of buoyage

The reference direction that decides which side is which — generally the direction you travel when approaching a harbour, river or estuary from seaward.

Topmark

A distinctive shape fitted to the top of a buoy or beacon, repeating the mark's message in a form you can read at a distance or in silhouette.

Every lateral mark only makes sense relative to the direction of buoyage — into the harbour when approaching from seaward, which is why the memory aids all say returning or entering. In open coastal waters it is set by convention: broadly eastward up the English Channel, northward up the Irish Sea, northward along the North Sea coast. Wherever it could be in doubt, the chart prints a broad magenta arrow — the authority.

Where a channel forks, one branch is usually the main route, and a preferred channel mark sits at the junction: a lateral mark in its main colour with one broad band of the opposite colour. Treat it as its main colour and you follow the preferred channel. Its light — a composite group flash, Fl(2+1) (two flashes, a pause, one more) — exists on no other kind of mark.

Cardinal marks answer a different question: not which side of the channel, but where the safe water lies relative to a danger, named by compass point.

Every cardinal is black and yellow with a topmark of two black cones, and the cones are the key. North: both up. South: both down. East: base to base (an egg). West: point to point (W for wineglass). The colours follow the cones — the cones point towards the black band. At night the lights are always white and quick (Q, about one flash a second) or very quick (VQ, about two), counting round a clock face: 3 flashes east, 6 south, 9 west, continuous north. South adds a long flash after its six, so a partly-counted west (9) can never be mistaken for a south (6).

Isolated danger mark

Black with red band(s), two black spheres topmark, white Fl(2) light — two flashes echoing the two spheres. A small danger with navigable water around it: pass well clear on any side, because the danger is directly beneath.

Safe water mark

Red and white vertical stripes, single red sphere topmark, white Iso, Oc, LFl 10s or Mo(A) light. Navigable water all round — often the landfall buoy where a buoyed channel begins.

Special mark

Yellow, optional yellow X topmark, yellow light. Marks a feature such as a racing mark, outfall or exercise area rather than a navigational danger — the chart says which.

Emergency wreck marking buoy

Blue and yellow vertical stripes, alternating blue and yellow light, yellow upright cross topmark. Laid over a new, still-uncharted wreck until permanent marks are established.