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What Do Lateral Markers Indicate? Things to Know!

Fact checked by William Hart

what do lateral markers indicate

The U.S. navigational aid system contains lateral, cardinal, and non-lateral markers that provide specific safety information. Boaters must know how to interpret them quickly and precisely.

What do lateral markers indicate? They are fixed on the sides of channels, river estuaries, and other waterways to mark their limits. Your boat must pass between a pair of red and green aids to ensure safety.

When you proceed towards the open sea, green aids mark the channel’s right side, and red ones mark its left. You must navigate so that green markers are on your starboard, and red ones are on your port side.

This article will explain lateral markers’ meaning and guide you to differentiate and interpret each type. Boating information markers are not at all confusing once you understand the system. Let’s explore!

Table of Contents

Things to Know About Lateral Markers


Lateral aids can be red, green, or both. While red and green markers usually come in pairs, buoys with both red and green bands (named preferred-channel aid) do not.

Red and green markers are positioned on the edges of a well-defined channel. Your boat should always pass between them. Meanwhile, you can pass a preferred-channel aid on both sides.

You might be familiar with the phrase “Red, right, returning,” which means that when you return to the shore, the red aids mark the right side of the channel. You should keep them to your starboard (right) side and green aids to your port side to position your boat in safe waters.

The system is used along with a conventional direction of buoyage. As you approach landmasses (e.g., harbors, islands, docks) that have lateral aids without route marks, navigate clockwise around the land mass.

Three Types of Lateral Navigation Aids

Lateral aids appear in multiple shapes and characteristics. They can be:

  • Buoys – floating aids that are anchored to the seabed. “Can” refers to cylindrical-shaped buoys. “Nun” refers to buoys with cylindrical shapes and conical tops.
  • Beacons – fixed structures, such as lighthouses. A beacon that carries a light is called Light and one without is Daybeacon.
  • Daymarks – informational signposts similar to road signs. They might carry flashing lights but are rather difficult to spot at night.

All green, red, and preferred-channel aids can show up as buoys, beacons, or daymarks.

1. Green lateral aids


What is the green buoy markers’ meaning? As you move towards open waters, they mark the right side of the channel; thus, you should keep them to your starboard side.

When you return or enter a channel from the open sea, green aids mark the left side of the waterway. You should navigate your boat so that they stay on your port side.

You can notice these aids by the following characteristics:

  • They can be square Daymarks, beacons, or can buoys.
  • Each green lateral aid carries an odd number. This number increases as you move closer to land. Numbers on beacons are green, and the numbers on buoys are white.
  • They can be lighted or unlighted. They display rapid green flashes or one long flash every few seconds if lit.

2. Red lateral aids


Red buoys and beacons are placed opposite green ones. When you see a red buoy, what should you do?

As you proceed toward the sea, they mark the channel’s left side. You should keep them to your port side.

As you return or head upstream, they signify the channel’s right side, meaning you must pilot your boat so that they stay on your starboard side.

Keep in mind these characteristics to spot them more easily:

  • They can be triangular Daymarks, beacons, or red cone-shaped buoy marks (nuns).
  • Each red aid carries an even number. This number increases as you move inland. The numbers on beacons are red, and the numbers on nuns are white.
  • They might be lighted or unlighted. If lit, they display red flashes.

3. Preferred-channel aids


It can be distracting to see an aid with both red and green bands when boating, but all you need to do is focus on the topmost color.

If you spot a preferred-channel aid that has a red band on top when returning:

  • Keeping the aid to your starboard side will put you in the preferred channel
  • Keeping the aid to your port side will put you in the secondary channel

If you see an aid with green on top when proceeding seaward:

  • Keeping the aid to your starboard will put your vessel in the primary waterway
  • Keeping the aid to your port side will put your vessel in the secondary waterway

On both channels, your vessel is safe. In addition, these navigational aids have the following characteristics:

  • They have a letter designation telling their names on the nautical chart.
  • While preferred-channel beacons and Dayboards carry red and green letters, buoys carry white letters.
  • They may show red or green lights depending on their topmost colors.


1. Who is in charge of the lateral buoy system?

The International Association of Lighthouse Authorities (IALA) is responsible for creating a network of navigational lights and buoys. They choose colors, shapes, lights, and letters.

The U.S. Coast Guard is responsible for maintaining and ensuring this network functions properly. If you notice a crashed or shifted aid, you should contact the Coast Guard.

However, there are many private navigation aids, which are usually mooring buoys or private property markers. These aids are owned and maintained by individuals.

2. What are range markers?

Don’t mistake range markers for lateral aids. Though they share similar colors, their shapes are distinctive. A range marker has a tall pillar shape.

Range markers (also called Dayboard ranges) come in pairs. When vessel operators observe a pair in line, they can tell whether the boat is on the channel’s centerline.

They appear in multiple colors; the most popular are green, red, white, and black. The colors do not affect their meaning.

3. What do non-lateral markers indicate?

For safe lateral markers boating, you should understand other types of markers.

Unlike lateral aids, non-lateral ones are not located on the edges of channels. They show up in multiple positions and are mainly for:

  • Signifying regulations within an area (no-wake zone, idle speed, speed limits)
  • Providing information (direction, swimming zone, anchorage area)
  • Warning about hazards (fishnet grounds, rocks, floating objects)

There are eight different types of non-lateral buoys. Feel free to read further on our website for the meaning of each one.


The question “What do lateral markers indicate?” concerns many new boaters. We hope our article helped you understand the U.S. intricate buoy system.

All in all, these red and green aids signify the edges of channels and let you know which sides you should pass on. Keep in mind the phrase “Red, right, returning” to avoid confusing one for the other.

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