The IALA buoyage system explained: buoys, beacons and their lights
What every mark means — lateral, cardinal, isolated danger, safe water, special and emergency wreck marks — with their colours, topmarks and lights, and the difference between IALA regions A and B.
- Region A (Europe, Africa, most of Asia, Australia): entering from seaward, red can-shaped marks are kept to port and green cones to starboard. Region B (the Americas, Japan, Korea, the Philippines) swaps the colours: “red right returning”.
- Cardinal marks show where the safe water is: pass north of a north cardinal, east of an east cardinal, and so on.
- Cardinal lights follow a clock face: east 3 flashes, south 6 plus a long flash, west 9; north flashes without a break.
Regions A and B
| Region A | Region B | |
|---|---|---|
| Where | Europe, Africa, most of Asia, Australia and New Zealand | North, Central and South America, Japan, the Republic of Korea, the Philippines |
| Port-hand mark | Red, can-shaped, red can topmark, red light | Green, can-shaped, green can topmark, green light |
| Starboard-hand mark | Green, conical, green cone topmark, green light | Red, conical, red cone topmark, red light |
| Memory aid | Entering: red to port, like the port sidelight | “Red right returning” |
Only the lateral marks differ between the regions. Cardinal, isolated danger, safe water, special and wreck marks are the same everywhere.
The direction of buoyage
“Port” and “starboard” marks are named for a vessel going in the direction of buoyage: entering a harbour, river or estuary from seaward. Along a coast the authorities set the direction — generally clockwise around a continent — and the chart shows it with a large arrow symbol. Going out to sea, everything is reversed: the red marks of region A are then on your starboard side.
All the marks
Light characteristics
| On the chart | Meaning |
|---|---|
| F | Fixed: a steady light |
| Fl | Flashing: the light is shorter than the darkness. Fl(2) — groups of two flashes |
| LFl | Long flash: a flash of at least 2 seconds |
| Q / VQ | Quick (50–60 flashes a minute) / very quick (100–120 a minute) |
| Iso | Isophase: light and darkness of equal length |
| Oc | Occulting: the light is longer than the darkness |
| Al | Alternating: the colour changes |
| Mo(A) | Morse code — here the letter A, · — |
| Fl(2+1) | Composite group: two flashes, then one |
| 10s | The period: the whole sequence repeats every 10 seconds |
So Q(6)+LFl 15s reads: six quick flashes, a long flash, the whole sequence every 15 seconds — a south cardinal mark.
Memory aids
- Cardinal topmarks: north — both cones point up; south — both point down; east — base to base, like an egg; west — point to point, like a wineglass.
- Cardinal colours: the cones point to the black. North: black on top; south: black below; east: black top and bottom; west: a black band in the middle.
- Cardinal lights: a clock face — 3 o'clock east, 6 south, 9 west, and north “all the time”.
- Isolated danger: two black balls, two flashes — a small danger with navigable water all round it.
- Safe water: red and white stripes, one red ball — the start of a channel or the middle of it.
- All yellow means a special mark, not a navigation mark: a cable, an outfall, a racing area, a swimming zone.
Test yourself
Seven questions from the Skipperium trainer, with the drawings. Choose your answer, then open the explanation.
1. What mark is this and on which side do you pass it?
- North — pass to the north
- South — pass to the south
- East — pass to the east
- West — pass to the west
Show the answer
Correct answer: A — North — pass to the north
Cones point up, black over yellow — north cardinal. Light white Q or VQ, continuous.
2. What mark is this and on which side do you pass it?
- North — pass to the north
- South — pass to the south
- East — pass to the east
- West — pass to the west
Show the answer
Correct answer: D — West — pass to the west
Cones point to point, yellow-black-yellow — west cardinal. Light white Q(9) or VQ(9).
3. What mark is this (IALA region A)?
- Isolated danger: keep clear all round
- Safe water: pass close by
- Special: a special area
- New wreck: keep clear
Show the answer
Correct answer: A — Isolated danger: keep clear all round
Isolated danger mark: black with a red band, two black balls, light white Fl(2). Keep well clear.
4. You are leaving the harbour for the sea (region A). On which side do you leave the green marks?
- To starboard
- To port
- Green marks are passed on the seaward side
- Whichever is convenient
Show the answer
Correct answer: B — To port
The direction of buoyage is from seaward into the harbour. On the way out everything is reversed: green marks to port, red to starboard.
5. In which IALA region are the red lateral marks on the starboard side when entering from seaward?
- In region A: Europe, Africa, Asia
- In region B: the Americas, Japan, Korea
- Everywhere: it is the same all over the world
- Only on the rivers and canals of Europe
Show the answer
Correct answer: B — In region B: the Americas, Japan, Korea
In region B the lateral colours are reversed: entering, red is to starboard (“red right returning”). Europe is region A: red to port.
6. Entering from seaward (region A), you see a red mark with a broad green band, light Fl(2+1) R. What is it?
- Isolated danger: keep clear all round
- Main channel to starboard: leave the mark to port
- Main channel to port: leave the mark to starboard
- Safe water: pass on either side
Show the answer
Correct answer: B — Main channel to starboard: leave the mark to port
A preferred channel mark — the channel divides. The main colour is red: following the main channel, you leave the mark to port like an ordinary red one; the main channel is to starboard. Light — group (2+1).
7. How does an occulting light (Oc) differ from a flashing one (Fl)?
- Oc shows light longer than dark, Fl shorter
- Oc is red, Fl is always white
- Oc works only by day, Fl only by night
- Not at all: they are two names for one light
Show the answer
Correct answer: A — Oc shows light longer than dark, Fl shorter
Occulting (NL onderbroken licht): light longer than dark, short eclipses. Flashing (NL schitterlicht): short flashes, dark longer. Isophase — light and dark equal.
Frequently asked questions
What is the IALA buoyage system?
The international system of buoys and beacons agreed through IALA. It has five kinds of marks — lateral, cardinal, isolated danger, safe water and special — plus the emergency wreck mark, each with its own colours, shape, topmark and light, so a mark can be read anywhere in the world.
Which side do I pass a red buoy on?
In region A (Europe and most of the world outside the Americas), keep red port-hand marks on your port side when entering from seaward, and on your starboard side when heading out to sea. In region B it is the other way round: red right returning.
What is the difference between IALA A and IALA B?
Only the colours of the lateral marks: in region A the port-hand marks are red and the starboard-hand marks green; in region B port-hand marks are green and starboard-hand marks red. All other marks are the same.
How do I remember the cardinal marks?
The cones point to where the black is, and the lights follow a clock face: east 3 flashes, south 6 plus a long flash, west 9, north continuous. You pass on the side the mark is named after.
What does a yellow buoy mean?
A special mark: a special area or feature such as a cable, a pipeline, an outfall, a racing or water-ski zone. It is not a navigational danger mark; check the chart for what it marks.
What is the direction of buoyage?
The direction in which the lateral marks are named: entering a harbour, river or estuary from seaward; along a coast as set by the authorities — generally clockwise around a continent — and shown on the chart by a large arrow.
What does a blue and yellow buoy mean?
An emergency wreck marking buoy: a new wreck not yet shown on charts. It has blue and yellow vertical stripes, an upright yellow cross on top and an alternating blue and yellow light. Keep well clear.
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