IALA buoyage system A (used in Europe, Africa, Australia and most of Asia). Lateral marks, cardinal marks, isolated danger, safe water and special marks — colours, shapes, topmarks and lights.
This guide covers IALA Region A. The USA, Japan and the Philippines use IALA Region B — where lateral mark colours are reversed. Always check which system applies to your cruising area.
Lateral marks define the sides of a navigable channel. Direction of buoyage generally follows the direction of the flood tide, or towards a port from seaward.
Mark
Colour
Shape
Topmark
Light
Meaning
Port hand
Red
Can / pillar / spar
Fl R
Keep to port — leave to port when travelling with the buoyage
Starboard hand
Green
Conical / pillar / spar
Fl G
Keep to starboard — leave to starboard when travelling with the buoyage
Preferred channel — port(secondary to starboard)
Red & green stripes (red top)
Can / pillar / spar
Fl(2+1) R
Junction / bifurcation — preferred channel is to starboard of this mark
Preferred channel — starboard(secondary to port)
Green & red stripes (green top)
Conical / pillar / spar
Fl(2+1) G
Junction / bifurcation — preferred channel is to port of this mark
Red is port, and red wine is left in the bottle — port (left) marks are red.
Cardinal marks
Cardinal marks indicate the safe side on which to pass a hazard — named after the compass direction of safe water from the mark.
Mark
Colours
Topmark
Light
Pass to…
North cardinal
Black over yellow
VQ or Q — continuous quick flashing
North of the mark
South cardinal
Yellow over black
VQ(6)+LFl or Q(6)+LFl — 6 quick flashes then long
South of the mark
East cardinal
Black–yellow–black
VQ(3) or Q(3) — 3 quick flashes
East of the mark
West cardinal
Yellow–black–yellow
VQ(9) or Q(9) — 9 quick flashes
West of the mark
The topmarks always point to the black band(s): North = black on top → cones up; South = black on bottom → cones down; East = black top and bottom → cones apart (egg timer); West = black in middle → cones together (wine glass).
Flash count by clock: North = 12 o'clock = continuous; East = 3 flashes; South = 6 flashes + long; West = 9 flashes.
Isolated danger mark
Marks a small, isolated danger with navigable water all around it. Do not pass close — give it a wide berth on all sides.
Colour
Shape
Topmark
Light
Black with red band(s)
Pillar or spar
Two black spheres
Fl(2) W — 2 white flashes
Two black balls = danger below — like two eyes staring up from the hazard beneath.
Safe water mark
Indicates navigable water all around — used for fairway / mid-channel marks and landfall buoys. Safe to pass on either side.
Colour
Shape
Topmark
Light
Red & white vertical stripes
Spherical / pillar / spar
Single red sphere
Iso W, Oc W, LFl W or Morse A (· —)
Red and white stripes = barber's pole = safe to approach — it's a fairway buoy welcoming you in.
Special marks
Mark a feature referred to in nautical documents — traffic separation schemes, military exercise zones, cable/pipeline areas, recreation zones, spoil grounds. Not primarily intended as navigational aids.
Colour
Shape
Topmark
Light
Yellow
Any shape not used by other marks
Yellow X
Fl Y — yellow light (any rhythm)
New dangers / emergency wreck marking buoy
Marks a newly discovered hazard (recently sunk vessel, newly charted rock) that may not yet appear on charts. Introduced by IALA in 2016.
Colour
Shape
Topmark
Light
Blue & yellow vertical stripes (equal)
Pillar or spar
Upright yellow cross
Al Fl Bu Y — alternating blue and yellow quick flash
At least one duplicate buoy is laid when used for a new danger. Both are removed once the hazard is charted.
Quick reference summary
Mark type
Colour
Light colour
Key action
Port lateral (Region A)
Red
Red
Leave to port (on your left) going with buoyage
Starboard lateral (Region A)
Green
Green
Leave to starboard (on your right) going with buoyage