Table of Contents

U.S. Aids to Navigation System (ATON)

Buoys and markers are the “traffic signals” that guide vessel operators safely along some waterways. They also identify dangerous or controlled areas and give directions and information. As a recreational boat or PWC operator, you will need to know the lateral navigation markers and non-lateral markers of the U.S. Aids to Navigation System.

Lateral Markers

These navigation aids mark the edges of safe water areas; for example, directing travel within a channel. The markers use a combination of colors and numbers, which may appear on either buoys or permanently placed markers.

Red colors, red lights, and even numbers indicate the right side of the channel as a boater enters from the open sea or heads upstream.

Red lateral marker

Red colors, red lights, and even numbers lateral marker

Green colors, green lights, and odd numbers indicate the left side of the channel as a boater enters from the open sea or heads upstream.

Green lateral marker buoy with green light and odd number

Green colors, green lights, and odd numbers lateral marker

Red and green colors and/or lights indicate the preferred (primary) channel. If green is on top, the preferred channel is to the right as a boater enters from the open sea or heads upstream; if red is on top, the preferred channel is to the left.

Red and green lateral marker

Red and green lateral marker

Nuns are red cone-shaped buoys marked with even numbers.

Cans are green cylindrical-shaped buoys marked with odd numbers.

Lighted Buoys use the lateral marker colors and numbers discussed above; in addition, they have a matching colored light.

Nun, can, and a buoy

A nun, a can, and a lighted buoy

Daymarks are permanently placed signs attached to structures, such as posts, in the water. Common daymarks are red triangles (equivalent to nuns) and green squares (equivalent to cans). They may be lighted also.

Green square and Red triangle daymarks

Green and red daymark

Red Right Returning is a reminder of the correct course when returning from open waters or heading upstream.

Red Right Returning boat enters a channel

Entering channel: red buoy on starboard, green on port

Intracoastal Waterway System

The Intracoastal Waterway (ICW) is a chain of channels that provide an inland passage along the U.S. coast. Buoys and markers used in this system are identified by yellow symbols and serve a dual purpose—they are navigational aids for the lateral system and are markers for the ICW.

If you are following the ICW from New Jersey to Brownsville, Texas, in a clockwise direction:

  • Any marker displaying a yellow triangle should be passed by keeping it on the starboard (right) side of your vessel.
  • Any marker displaying a yellow square should be passed by keeping it on the port (left) side of your vessel.
Intracoastal Waterway Markers

Intracoastal Waterway (ICW) Markers

Non-Lateral Markers

Non-lateral markers are navigational aids that give information other than the edges of safe water areas. The most common are regulatory markers which are white and use orange markings and black lettering (shown below). These markers are found on lakes and rivers.

Information

Squares indicate where to find food, supplies, repairs, etc. and give directions and other information.

Controlled

Circles indicate a controlled area such as speed limit, no fishing or anchoring, ski only or no skiing, or “slow, no wake.”

Exclusion

Crossed diamonds indicate areas off-limits to all vessels such as swimming areas, dams, and spillways.

Danger

Diamonds warn of dangers such as rocks, shoals, construction, dams, or stumps. Always proceed with caution.

Information, controlled, exclusion, and danger non-lateral markers

Information, controlled, exclusion, and danger non-lateral markers

Other Non-Lateral Markers

Safe Water Markers are white with red vertical stripes and mark mid-channels or fairways. They may be passed on either side.

Inland Waters Obstruction Markers are white with black vertical stripes and indicate an obstruction to navigation. You should not pass between these buoys and the nearest shore.

Mooring buoys are white with a blue horizontal band and are found in marinas and other areas where vessels are allowed to anchor.

Non-lateral marker of the U.S. Aids to Navigation System (ATON): Safe Water Markers are white with red vertical stripes and mark mid-channels or fairways. They may be passed on either side.

Safe water marker, inland waters obstruction, and a mooring buoy

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