Buoys and marks

The U.S. Aids to Navigation System (33 CFR Part 62) gives every buoy and beacon a colour, a shape, and often a number and a light. Read them in order: colour first, then shape, then number and light.

Red right returning

Heading in the Conventional Direction of Buoyage (in general, coming in from sea or heading upstream; the chart settles it), keep red marks on your right and green marks on your left. Red buoys are cone-topped "nuns" and carry even numbers; green buoys are flat-topped "cans" and carry odd numbers. Numbers increase as you go in. Lights follow the same rule: red lights on red marks, green on green.

Junctions

A buoy with red and green horizontal bands marks where a channel splits. The top band names the preferred channel: green on top, treat it as a green mark; red on top, treat it as a red mark.

Marks that are not red or green

• Red and white vertical stripes: safe water, navigable water all around.
• Black with a red band and two black balls on top: an isolated danger you can pass on any side; do not go close.
• Solid yellow: a special mark for an area shown on the chart (anchorage, cable area and so on).
• White with a blue band: a mooring buoy.
• Black and white vertical stripes (state inland waters): an obstruction runs from shore to the buoy; do not pass between them.

Orange on white: information and regulatory marks

• Open diamond: danger.
• Diamond with a cross: boats keep out.
• Circle: operating restrictions, such as a speed limit or no wake.
• Square or rectangle: information, such as directions.

Two exceptions to know about before you rely on the rule: the Intracoastal Waterway adds yellow triangles and squares that can override the colour, and the Western Rivers use their own variation. Check the chart.