Buoyage

The marks that mark the channel (IALA-A / SIGNI).

The two systems

Lateral — the sides

Marks the sides of the channel. Green = starboard side (conical), red = port side (can/cylindrical). Rule of thumb when heading upstream: green to starboard, red to port.

Cardinal — relative to a danger

Uses the compass direction (north/east/south/west) to show where the safe water is relative to a danger. Always black-yellow with black cone topmarks; the cones point to the black band.

On the river — step by step

Step 1 of 6

The river and the current

Which bank is 'left' and 'right' is always determined looking downstream (towards the sea). Your right hand then points to the right bank. Here the water flows downward, so the right bank is on the left of the image.

Light characters — the flashing lights

At night you recognise marks by their light character: the rhythm of on and off. The light/dark ratio defines the type.

📖 Reading a code like VQ(3) 5s: VQ = very quick flashing, (3) = three flashes per group, 5s = the whole group + pause repeats every 5 seconds (the period).

The types (with memory aids)

IsoIsophase

Meaning: On as long as off.

💡 Remember: “iso” = equal (as in isotherm) → light and dark are equal.

OccOcculting

Meaning: On longer than off — the light is briefly interrupted.

💡 Remember: “occult” = hidden/covered (Latin occultare). The light is briefly covered.

FlFlash

Meaning: On shorter than off — a brief flash.

💡 Remember: A short “flash” in the dark → on shorter than off.

LFlLong flash

Meaning: One flash of at least 2 seconds.

💡 Remember: “Long”: the flash lasts ≥ 2 s.

QQuick

Meaning: Quick flashing — about once per second.

💡 Remember: Quick = fast. Many cardinals flash Q or VQ.

VQVery quick

Meaning: Very quick — about twice per second.

💡 Remember: VQ is twice as fast as Q.

Cardinal marks — count with the clock

Each cardinal mark carries a white light. The number of flashes follows the clock: east = 3 o'clock (3), south = 6 (6), west = 9 (9), north = 12 (continuous). The animation shows the VQ rhythm; the bar is exactly one period and the white head runs in sync with the lamp.

North — VQ or Q, continuous (12 o'clock)

period: continuous (no pause)

VQ rhythm, period —

East — VQ(3) 5s or Q(3) 10s (3 o'clock)

period: 5 s

VQ rhythm, period 5 s

South — VQ(6)+LFl 10s or Q(6)+LFl 15s (6 o'clock)

period: 10 s

VQ rhythm, period 10 s

West — VQ(9) 10s or Q(9) 15s (9 o'clock)

period: 10 s

VQ rhythm, period 10 s

All marks & buoys

Tap “More info” to see what a mark means relative to the danger.

Starboard mark (lateral)

Green, conical. Keep it to starboard when heading upstream.

When heading upstream you keep this green mark to starboard (your boat's right).

Port mark (lateral)

Red, can (cylindrical). Keep it to port when heading upstream.

When heading upstream you keep this red mark to port (your boat's left).

Safe water

Red-white vertical stripes, red sphere. Safe water all round; pass either side.

There is safe water all around. You may pass on either side — often it marks mid-channel or a landfall.

Junction mark (main/side fairway)

Spherical buoy with red and green. Marks the split between main and side fairway.

Cardinal — North

Black over yellow, two cones up. Pass to the north.

The danger is to the south of the mark. So the north mark sits north of the danger — pass to the north. The two cones point up (north / safe water).

Cardinal — East

Black-yellow-black, cones base to base. Pass to the east.

The danger is to the west of the mark. Pass to the east. The cones are base to base (round, like an egg = East).

Cardinal — South

Yellow over black, two cones down. Pass to the south.

The danger is to the north of the mark. Pass to the south. The two cones point down (south / safe water).

Cardinal — West

Yellow-black-yellow, cones point to point. Pass to the west.

The danger is to the east of the mark. Pass to the west. The cones are point to point (narrow waist = West).

Isolated danger

Black with red band(s), two black spheres. Marks an isolated danger.

The mark lies on top of an isolated danger (e.g. a wreck or shoal). There is safe water all around — stay clear of the mark. Two spheres are the key feature.

Special mark

All yellow, with a yellow cross (X) topmark. Marks no channel, but a special area or object (e.g. cables/pipelines, a recreation or measuring zone). Light, if any: yellow.