Notice - The images and information on this page is presented for your convenience as an educational tool. It's not the intended that this information replace other navigational aids and sources. The wise sailor doesn't rely on any single aid to navigation or information source. For additional information on the topic of navigational aids we suggest the latest volume of the U.S. Department of Transportation's Light List, available from Torresen Marine, Inc.

Port Side (odd numbered) Aids

These cylindrical bouys are often referred to as can bouys. The can bouy is usually solid green in color. They may also contain an off-green colored reflector. The can bouy will mark the left side of the channel when proceeding from seaward. In the past the can bouy was painted black in color with a green reflector.

The green lighted bouy serves the same function as the non-lighted green can. They tell the mariner the margin of the port side of channels and mark wrecks or obstructions which must be past by keeping the aids to navigation on the port side of the vessel.

The square daymark is green in color. It will usually contain two colors of green. One shade of green for the square interior and another green as a reflective outline. This dayboard is used to mark the port (left) side of channels when proceeding from seaward. Daymarks are mounted on a pole, or other structure to hold them above the waterline. Some daymarks will also have a light above them.

When bouys are bi-colored they mark the start of two channel choices. The upper most color marks the preferred choice. Those markers with a top color of green signify a starboard preferred channel. Those markers with a top color of red signify a port preferred channel.

Starboard Side (even numbered) Aids

The conical shaped red bouys are known as nuns. Nun bouys mark the right side of the channel when proceeding from the seaward. These aids to navigation are commonly associated with a solid red color. They may also include an off-red color reflector.

The red lighted bouy serves the same function as the non-lighted red nun. They tell the mariner the margin of the starboard side of channels and mark wrecks or obstructions which must be past by keeping the aids to navigation on the starboard side of the vessel.

The triangular daymark is red in color. It will usually contain two colors of red. One shade of red for the triangle interior and another red for the reflective outline. This dayboard is used to mark the starboard (right) side of channels when proceeding from seaward. Daymarks are mounted on a pole, or other structure to hold them above the waterline. Some daymarks will also have a light above them.

When bouys are bi-colored they mark the start of two channel choices. The upper most color marks the preferred choice. Those markers with a top color of green signify a starboard preferred channel. Those markers with a top color of red signify a port preferred channel.