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Preferred channel marks

Where a channel divides, a modified lateral mark is placed, with one broad horizontal band in the other colour. The base colour points to the preferred (main) channel, and the distinctive Fl(2+1) light separates it from an ordinary lateral mark.

Region A, preferred channel to starboard

Colour
horizontal bands: red, green, red
Buoy shape
can (cylindrical)
Topmark
a single cylinder (can)
Light
Fl(2+1) A group of two flashes, then one more, then a pause. The preferred channel rhythm.
What it means
The preferred channel goes to starboard. Leave the mark on your port side.

Region A, preferred channel to port

Colour
horizontal bands: green, red, green
Buoy shape
conical (nun)
Topmark
a single cone, point up
Light
Fl(2+1) A group of two flashes, then one more, then a pause. The preferred channel rhythm.
What it means
The preferred channel goes to port. Leave the mark on your starboard side.

Region B, preferred channel to starboard

Colour
horizontal bands: green, red, green
Buoy shape
can (cylindrical)
Topmark
a single cylinder (can)
Light
Fl(2+1) A group of two flashes, then one more, then a pause. The preferred channel rhythm.
What it means
The preferred channel goes to starboard. Leave the mark on your port side.

Region B, preferred channel to port

Colour
horizontal bands: red, green, red
Buoy shape
conical (nun)
Topmark
a single cone, point up
Light
Fl(2+1) A group of two flashes, then one more, then a pause. The preferred channel rhythm.
What it means
The preferred channel goes to port. Leave the mark on your starboard side.

Facts per the IALA Maritime Buoyage System (MBS ed. 2.0). The drawings are our own vectors. The light rhythm and colour in the drawing are illustrative: check the real characteristics of a specific buoy on the chart and in the list of lights.