Navigation 101

Basics of Navigation 

In contrast to the roads and highways we drive on, waterways do not have signs telling us where we are, how far we are from a destination, or if there are hazards. 

Waterways are equipped with AIDS TO NAVIGATION (Or ATONs), manufactured objects mariners use for navigation. These aids help mariners make a safe landfall, mark isolated dangers, guide pilots along channels, and help them navigate precisely. An aid to navigation is any visual, audible, or electronic symbol established by the government or private authorities to assist navigation. 

Boaters use the Federal Aids to Navigation System (USATONS) and the State Waterway Marking System (USWMS) to determine their position and course and to avoid hazards or obstructions. 

USATONS is a system for marking navigable waters with regulatory markers and aids to navigation. For navigable state waters, USWMS prescribes regulatory markers and aids in navigation. 

Lateral Aids to Navigation

nautical map

Several citations are issued regularly for failure to abide by regulatory markers. Experienced boaters know how to recognize and respond to all USATONS and USWMS aids and systems, so they can navigate safely and be aware of any potential dangers.

As a result of completing this section, operators should be able to recognize and explain the different buoy functions and respond accordingly to the specific concerns identified by the navigational aids. 

Types of Aids to Navigation

An aid to navigation refers to a wide range of fixed and floating objects, which include buoys and beacons. 

Buoys are items that float on the water’s surface but are anchored to the bottom. Shapes and colors distinguish them from one another and help determine their purpose.

Beacons are structures that are permanently anchored to the seabed or land. Structures such as lighthouses and single-pile poles can be included in this category. Beacons that are lighted are called “LIGHTS,” while unlighted beacons are called “DAYBEACONS.”

Buoys and Beacons may have lights attached and a sound-making device such as a gong, bell, or horn. Both Buoys and Beacons may be called “marks.”

If you are boating in America, you may notice several differences in the color, number, or illumination of navigational marks. It is always important to note that buoys and beacons are positioned at precise locations to indicate a particular side of a waterway or some other navigation feature. This system is called the “US Aids to Navigation System.” 

According to the US Coast Guard, this system is maintained by the International Association of Lighthouse Authorities (IALA), an international association dedicated to ensuring safe navigation, primarily using common navigation aids and signals.

USATONS Lateral Buoy System

map of buoys

A “LATERAL” system is similar to the RED RIGHT RETURNING system since the red even-numbered marks are found on the right side of the channel on all navigable waters returning from sea, while the green odd-numbered marks are on the left side. 

As you travel from sea to harbor, the buoy numbers on the marks will ascend, indicating you are heading upstream. Even when you become disoriented in the water without a compass, you will always be able to tell where you are if the buoy numbers are increasing.

Upstream Direction (“3R” Red Right Returning Rule)

upstream chart

Using the mnemonic phrase “red, right, returning” is an effective way for boaters to remember how to use the lateral buoys. The purpose of this simple phrase is to remind the boater which side of the vessel the buoys should be on when traveling upstream or downstream. 

When returning upstream, the boater should keep the red buoys on the boat’s right (starboard) side. A number is assigned to each aid, which increases as the aid approaches the seaward side. An “upstream” direction moves up-stream, toward the shoreline, or towards a harbor. Additionally, it describes the movement from an open body of water to a more restricted area

Port Side (Odd-Numbered) Aids

The port side numbered aids are green, odd-numbered, and lighted. As you travel upstream, you will encounter port side markers on your left and buoy numbers increasing as you progress. 

port side navigation aids

The port side buoy appears like a cylindrical object floating on its axis above the water. This type of buoy is commonly referred to as a “CAN” buoy. The port side beacons are marked with two shades of color and have a reflective border around them. 

Starboard Hand 

Starboard Side Aids are also known as “right hand” aids and are red in color. As vessels travel upstream, these aids mark the right side of the channel. They should be kept to the right of the vessel (starboard). 

starboard side aids

As seen above water, Starboard-Side Buoys look like cylinders topped with cones, with the pointed end upward. The Starboard-side Beacons have two shades of color and a reflective border with triangular marks. 

Preferred Channel Marks

Typically, preferred channel markers are located at the junction of navigable channels, indicating wrecks and obstructions. Preferred Channel Marks can be passed on either side. However, the color of the top band suggests which of the two channels is the safest. A red band at the boat’s top is considered a red aid and should be maintained to the starboard side as the boat passes. Passing on both sides of Preferred Channel Aids is not always possible.

boating navigation aids

Non-Literal Aids / Marks to Navigation


A dayboard is a diamond-shaped indicator that helps the boat operator determine their location on the water. Its purpose is similar to building maps with “You Are Here” markings. Using nautical charts with dayboards is essential for determining the vessel’s location.

Safe Water Marks

Safe Water Marks identify fairways, mid-channels, and offshore approach points. In addition to being lettered, these marks can be illuminated with white light. There may also be a red top mark on them. Additionally, boaters traveling in offshore waters may be able to identify the proximity of intended landfall using these marks.

safe water navigation marks

Isolated Danger Marks

As their name indicates, Isolated Danger Markers indicate a potential danger that may be seen from any direction. Considering that they are often located on or near hazards, it is not recommended that you approach them closely without exercising extreme caution.

isolated danger mark

Range Dayboards

Range Dayboards function as navigation aids when used in pairs. By aligning the dayboards with each other, boaters can maintain a safe course within a navigable channel. It is necessary to consult a nautical chart to determine whether boaters can safely travel a range. These range dayboards can be lighted or unlighted. 

Regulatory Marks

Regulatory Marks are also called Informational Marks. Boaters can use these terms interchangeably. These aids assist boaters by marking danger areas, identifying special restrictions, and determining which controlled areas are approaching. They are characterized by black text and orange symbols and, if lighted, may display any light rhythm. 

navigation marks

Danger Markers

The Danger Markers have an orange diamond shape, and their purpose is to alert boaters to hazards that may be present. 

  • Restricted Operations Marker
  • Boat Exclusion Area Marker

Miscellaneous Aids 

Mooring Buoys 
mooring buoy

Only mooring buoys are permitted to be attached to boats legally. The shape of mooring buoys can be either spherical or cylindrical. These buoys have white bodies with a blue horizontal band in the middle. In most cases, they are equipped with a white reflector. 

Special Marks

Special Marks identify features or areas that are unique, such as anchoring sites, fishnet areas, cables and pipelines, military exercise zones, jetties, etc. Boaters do not need to pay attention to special marks for navigational purposes.

Inland (State) Waters Obstruction Marks
Inland waters obstruction mark

Inland Waters Obstruction Marks are buoys that alert boaters to obstructions to navigation within a specific distance from the shore. There are vertical stripes of black and white on each of them.



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