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The IALA Maritime Buoyage System (IALA MBS) is the global standard for navigation marks at sea. It was unified in 1980 from earlier divergent systems and divides the world into two regions for the colour of lateral marks: Region A (most of the world — Europe, Africa, the Gulf, Asia, Australasia) uses red to port, green to starboard. Region B (the Americas, Japan, Korea, the Philippines) uses the opposite — green to port, red to starboard. The colour and shape of cardinal, isolated danger, safe water, and special marks are the same in both regions.
The direction of buoyage in a harbour is "from seaward" — when entering. On a chart it is shown by a magenta arrow. In coastal waters the direction generally runs clockwise around continents in the northern hemisphere and is given on the chart explicitly where it would otherwise be ambiguous.
Leave to port when entering harbour from seaward.
Leave to starboard when entering harbour from seaward.
Leave to port when entering harbour from seaward ("red right returning" — opposite of Region A).
Leave to starboard when entering harbour from seaward.
In Region B the colour scheme is reversed.
Bifurcation; preferred channel goes to starboard. Treat the mark as a port-hand mark of the preferred channel.
Bifurcation; preferred channel goes to port. Treat the mark as a starboard-hand mark of the preferred channel.
Topmarks are the most reliable cue: the points of the cones "point" toward the side that has black on the buoy. North = both up; South = both down; East = points apart (out); West = points together (in).
Pass to the north of the mark; safe water lies north.
Pass to the east of the mark; safe water lies east.
Pass to the south of the mark; safe water lies south.
Pass to the west of the mark; safe water lies west.
Stationed on, moored to, or above an isolated danger of limited extent which has navigable water all around it.
Navigable water all around; mid-channel, fairway, or landfall mark.
Indicates a special area or feature whose nature is shown on the chart: spoil grounds, military exercise areas, cables and pipelines, ODAS and traffic separation marks where conventional buoys cannot be used.
Newly discovered hazard not yet shown on charts. Pillar or spar buoy, equal vertical blue and yellow stripes, yellow upright cross topmark.
Diagrams are simplified schematics intended as a memory-aid. For passage planning use the chart, the relevant List of Lights, and current Notices to Mariners.