#nautical navigation

Channel Markers are aids to navigation in harbors. These buoys mark the shipping channels in a harbor. You can think of as them as the nautical equivalent of lanes on a roadway. In US waters, channel markers come in two colors, green (known as “cans”), and red (known as “nuns”).

Cans are flat on top and are painted with odd numbers and mark the port (left-hand) side of the shipping lanes when a vessel is entering the harbor from the sea or heads upstream, and the starboard (right-hand) side of the lanes when a vessel is leaving the harbor/going downstream/returning to sea. Nuns are conical on top and are painted with even numbers and mark the starboard side of the lanes for a vessel entering a harbor or the port side for a vessel leaving the harbor. There are also red and green buoys that mark junctions at the channels. These buoys are usually on nautical charts, so knowing what they mean is important for reading charts as well as for actually boating.

A handy memory aid to remember which marker means what is “Red, Right, Returning.”

Entrances of harbors are marked with red or green lighted buoys, each of which has a unique flashing pattern that shows up on charts for ID purposes. These are useful for navigating at night.

Below is a helpful illustration, courtesy the US Coast Guard, showing each of these plus how they show up on charts: