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IALA Region A vs Region B — what actually changes
Two regions, one global system. The IALA Maritime Buoyage System is identical worldwide except for one detail — the colour of lateral marks. That single inversion is responsible for more exam mistakes than any other IALA topic.
This page lays the two regions side-by-side: the lateral-mark colour swap, the memory aid that survives both, the list of countries on each side, and what stays the same regardless of where you sail.
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Region A vs Region B — side-by-side
| Aspect | Region A | Region B |
|---|---|---|
| Port-hand lateral mark | RED can / cylinder | GREEN can / cylinder |
| Starboard-hand lateral mark | GREEN cone | RED cone |
| Memory aid (returning from sea) | Red on your LEFT — "red port leaving" | Red on your RIGHT — "red right returning" |
| Preferred-channel mark (port preferred) | Red with green band, red can topmark | Green with red band, green cone topmark |
| Cardinal marks N · E · S · W | Identical | Identical |
| Isolated danger mark | Identical — black with red bands, two black spheres | Identical |
| Safe water mark | Identical — red/white vertical stripes | Identical |
| Special marks | Identical — yellow with yellow X topmark | Identical |
| Emergency wreck marking buoy | Identical — blue/yellow vertical stripes | Identical |
| Countries (examples) | UK · Spain · France · Italy · Greece · Croatia · Germany · India · Australia · South Africa | USA · Canada · Mexico · Brazil · Japan · South Korea · Philippines |
Which region am I in?
The fast answer: if you're sailing in the Americas, Japan, Korea, or the Philippines you're in Region B; everywhere else (every European coast, every African coast, India, Indonesia, Australasia) you're in Region A.
- Region B (red right returning): USA, Canada, Mexico, all of Central and South America, Japan, South Korea, Philippines.
- Region A (red on your left when returning): the entire European Atlantic and Mediterranean, all of Africa, India, Southeast Asia (except Japan/Korea/Philippines), Indonesia, Australia, New Zealand.
- When you cross a boundary by sea (e.g. cruising from Japan to Russia), the lateral-mark colour swaps the moment you enter the next state's waters — chart your transit accordingly.
- If in doubt mid-passage, check the chart's general notes — every chart states which IALA region it covers.
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Frequently asked questions
Is the United States in IALA Region A or Region B?
The United States is in IALA Region B. So are Canada, Mexico, all of Central and South America, Japan, South Korea and the Philippines. "Red right returning" is the Region B memory aid: when you are returning from sea into port, red lateral marks should be on your right (starboard) side.
What is the difference between IALA Region A and Region B?
Only the colour of the lateral marks. In Region A the port-hand mark is red and the starboard-hand mark is green. In Region B they are swapped. Cardinal marks, isolated-danger marks, safe-water marks, special marks and emergency wreck marks are identical in both regions worldwide.
Does Europe use Region A or Region B?
All of Europe — every Atlantic coast, the entire Mediterranean, the Baltic and the Black Sea — is in IALA Region A. So is the United Kingdom, despite Brexit; IALA is a technical convention administered by national maritime authorities, not the EU.
What is a preferred-channel mark?
A modified lateral mark that signals a junction: one channel is preferred over the other. In Region A: a port-preferred channel is marked red with a green horizontal band and a red can topmark. In Region B the colours are inverted (green with red band). The base colour is the mark you treat it as.
Do cardinal marks differ between Region A and Region B?
No. The four cardinal marks (North, East, South, West) are black-and-yellow in every IALA-signatory country, with identical topmark configurations and identical light rhythms (continuous quick or very quick flashing for N, plus 3 / 6+long / 9 flashes for E / S / W respectively). The only inter-regional difference is in lateral marks.
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