Understanding Marine Buoys: Navigation, Light Patterns, and Special Markings

Sailing In Style
5 min readAug 13, 2023

Navigating maritime waters demands a mastery of various visual cues, especially when safety is paramount. Buoys play a crucial role in this, signaling underwater dangers, safe passage routes, and marking specific areas of interest. Here’s a thorough understanding of their designs and meanings.

What are Buoys?

Buoys are anchored, floating markers that play a crucial role in maritime navigation. Their purpose spans from indicating submerged hazards and safe navigational paths to specifying special areas. Many are equipped with lights and sound signals, enhancing their visibility and interpretability.

The Color Code

Green Buoys

Often termed “starboard hand buoys”, these mark the channel’s right side when moving towards the shore or heading upstream. They may flash a green light. Example: Entering a harbor, you’d keep these on your right.

Red Buoys

Otherwise known as “port hand buoys”, they signify the left side of a channel from the open sea or when traveling upstream. Typically, they may flash a red light. Example: Navigating a river mouth from the sea, these should be on your left.

Red and Green Banded Buoys

Indicating the center of a channel, the topmost band denotes which side to pass on. They may have a combination of red and green lights.

Cardinal and Safe Water Marks

Cardinal marks provide direction references, pointing towards the safest water based on the cardinal points — North, South, East, and West.

North Cardinal: Safe water lies to the North.
Visually: two black cones point upwards
Light rhythm: continuous flashing

South Cardinal: Indicating safe water to its South
Visually: Displays two black cones pointing away from each other.
Light rhythm: six flashes followed by a long flash.

East Cardinal: Safe water is on the East side
Visually: A black cone pointing up above another pointing down.
Light rhythm: three flashes in quick succession.

West Cardinal: Safe water to the West
Visually: Two black cones have their bases together.
Light rhythm: nine flashes in quick succession.

Safe Water Mark: A white buoy with red vertical stripes, this mark indicates waters clear of dangers from all sides. It’s also used to mark fairways, mid-channels, or landfalls. Some might be equipped with a single red ball on top as a daymark.
Light rhythm: a long flash followed by three short flashes.

Additional Buoys to know about

Yellow Buoys

Special purpose buoys, they can represent various scenarios like a military exercise zone or a seaplane base. Light rhythm can vary based on the specific purpose, but is always different from standardized light marks.

Orange and White Buoys

These regulatory markers, usually square or diamond-shaped, convey information like speed limits or specific warnings. Their light rhythms can vary based on the specific regulations they indicate.

Weather Buoys

An integral part of marine safety and research, weather buoys are specialized devices floating on the ocean’s surface, primarily designed to collect and transmit valuable atmospheric and oceanographic data. These buoys help sailors, researchers, and meteorologists understand weather conditions, ocean currents, and other marine-related phenomena.

Tidal Buoys

Tidal Buoys are a subset of oceanographic buoys specifically designed to monitor and provide data about tidal movements and sea level changes. Given the immense significance of tides in marine navigation, fishing, coastal management, and even renewable energy extraction, tidal buoys play a crucial role in various marine sectors.

Diving Buoys

These are used to indicate that diving operations are currently taking place in the area, and often shown as a white buoy with a red flag (or the Alpha flag, a blue and white flag, in international waters). The red flag has a diagonal white stripe from the top left to the bottom right. Vessels are advised to stay clear in a radius of 100 meters of the area or proceed with extreme caution when they see a diving buoy.

Light: If equipped, a diving buoy may have a flashing yellow light.
Rhythm: Rapid flashes, typically to warn that divers are at work.

Grounding Buoys or Shoal Buoys

These buoys indicate the presence of shallow waters or hazards beneath the surface, such as sandbanks or rock formations. They might have a variety of appearances depending on the region, but they often have specific markings or colors to indicate the nature of the hazard. These are critical for the safety of vessels, ensuring they don’t run aground or hit submerged hazards. If you see one or more of those, make sure you stay out of that zone and check the surroundings with your depth radar, fish finder or a rope with a weight and knots for the meters (the traditional way).
Light: These may have a white flashing light.
Rhythm: Could be a group of two flashes, symbolizing “caution.”

Isolated Danger Buoys

Used to mark small, isolated dangers such as a single rock or wreck. These buoys are black with one or more horizontal red bands. They might also have an accompanying light. They inform mariners of hazards in an area that is otherwise safe to navigate around.

Light: White light.
Rhythm: Group of two flashes, indicating the presence of an isolated danger nearby.

Restricted Area Buoys

Indicate areas where boating is temporarily restricted. It could be for environmental protection, swimming areas, or any other reason. Varies by region. In some areas, these buoys might be white with a black band and carry a specific symbol indicating the type of restriction. Helps in protecting sensitive marine areas, swimmers, or specific zones from vessel traffic. Also often used to mark fish farms.
Light: White or yellow, depending on the specific restriction.
Rhythm: The rhythm may vary based on the type of restriction. For instance, a buoy marking a swimming area might have a long flash every few seconds.

Cable and Pipeline Buoys

They mark the locations of underwater pipelines or cables. Typically yellow in international waters with the letter “C” on them. Prevents vessels from anchoring in areas where they might damage submerged infrastructure.
Light: Yellow light.

Rhythm: Typically two flashes every 5 seconds or so, indicating caution for the submerged infrastructure.

Regulations and Practical Uses

While buoys provide navigational guidance, sailors must resist the temptation to use them as anchor points. Anchoring to them is prohibited and can be dangerous due to the underwater mooring chain. Moreover, it could interfere with their primary purpose of guiding other vessels.

Last Words

A buoy isn’t just a floating object; it’s a storyteller of the seas, narrating tales of safe passages, treacherous obstacles, and special zones. Understanding their language is vital for sailors. Safe and informed sailing to all!

Originally published at https://www.sailinginstyle.com on August 13, 2023.

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