Various types of buoys play an indispensable role in the maritime world. They serve as important markers and signs that seafarers use to navigate the seas, channels, and fairways.

There are so many kinds of them, but these distinctions help mariners discern the purpose and meaning of their placement.

I realized the importance of buoys and identifying their types early on in my career when we got into an accident during maneuvering.

After that, I quickly delved into deep research about buoyage systems and the many different floating markers we use when navigating.

What are buoys?

Buoys are floating markers anchored to the seabed to aid marine navigation, collect data, and mark channels, hazards, or locations. They come in various shapes, sizes, and colors and display unique light signals, symbols, and markings.

The primary purpose of these floating markers is to enhance safety at sea. They guide vessels by indicating safe or hazardous waters and channel limits. 

Buoys also mark wrecks, reefs, tide or current information, scientific measurements, and traffic separation zones. We always watch these symbols in the nautical chart and their actual position on the sea to ensure we’re sailing on safe waters.

All types of buoys you may encounter at sea

Many types of buoys indicate specific purposes or” instructions” to seafarers. I’ve written a detailed article about them in my post, “The IALA Buoyage Systems – Best Easy-to-Understand Guide“.

But here, we’ll focus on the different types and their intended purpose. Aside from the directional and warning marks of the IALA System, this post will also tackle other special marks we encounter from time to time.

Cardinal Buoys

Cardinal marks indicate the direction of safe water in relation to a hazard. 

These floating markers divide the surrounding waters into four quadrants, each corresponding to one of the cardinal points on a compass – North, East, South, and West.

The Cardinal Marks North, South, East and West showing location relative to the Point of Interest.
Cardinal Marks.

1. North Cardinal Buoys

It is colored black above yellow and has two cones pointing upwards. It indicates that safe water lies to the North of the mark.

2. East Cardinal Buoys

Colored black-yellow-black on its body with two cones pointing away from each other. It indicates that safe water lies to the East of the mark.

3. South Cardinal Bouys

It is colored yellow above black and has two cones pointing downwards. It indicates that safe water lies to the South of the mark.

4. West Cardinal Bouys

Its body has a yellow-black-yellow color, with two cones pointing at each other. It indicates that safe water lies to the West of the mark.

Lateral Marks

Lateral marks indicate the port and starboard side of the channel in the direction of the conventional flow of the voyage. It’s easy to spot them because they use red and green colors.

Using these marks depends on the region, either Region A or Region B. Region A sets red buoys on the port side and green buoys on the vessel’s starboard side when she is inbound at a port or terminal.

It’s the opposite when outbound and vice versa in Region B.

5. Port Hand Buoy

Marks the left side of a channel when entering from seaward (Region A).

6. Starboard Hand Buoy

Marks the right side of a channel when entering from seaward (Region A).

7. Preferred Channel Buoy

Also known as Bifurcation Buoy, it indicates the preferred route in a channel with bifurcations or dividing of a channel into two branches.

  • Lateral marks for IALA Buoyage Region A showing their shapes color, light flashes, and the direction of the buoyage.
  • Lateral marks for IALA Buoyage Region B showing their shapes color, light flashes, and the direction of the buoyage.

8. Isolated Danger Marks

Isolated Danger Marks (IDM) indicate the presence of a specific hazard or obstruction with safe waters surrounding it. 

They warn mariners about a singular danger in the vicinity and are placed directly on or moored near the hazard they are marking.

IDMs have color black-red-black bands horizontally with two black balls in vertical lines as their top marks

An isolated Danger Mark having a color of black and red bands with two black balls on its top marks.
Image: Wikimedia.

9. Safe Water Marks

A safe water mark indicates navigable waters around the mark. They are usually installed as a landfall buoy, mid-channel mark, centerline mark, or to point to the best area of passage in a fixed bridge.

It has a red and white vertical stripe, either shaped as a spar or pillar, with a single red sphere as a top mark.

A Safe Water Mark having red and white vertical stripes.
Image: David Dixon

10. Emergency Wreck Marking Buoys

These floating markers indicate new dangers yet to be shown on nautical charts. They are deployed within the first 72 hours of the wreckage.

These marks have blue and yellow stripes with an upright yellow cross top mark.

A ship passing close by an Emergency Wreck Marking Buoy with yellow and blue stripes and a marking that says "WRECK".
Emergency Wreck Marking Buoy.

Special Marks

These buoys make up the most types, and checking the relevant nautical charts for their intended purpose is crucial.

Special marks are usually yellow-colored buoys with an “X” top mark (also yellow), but some may not share the same feature.

Reading the charts should give you more details about the nature of these marks.

11. Anchorage Buoy

Marks an area suitable for anchoring.

12. Mooring Buoy

Marks the location of tie-up points for vessels for mooring operations.

A mooring buoy shaped like a barrel having yellow and black color.
Image: Ian Paterson.

13. Swimming Area Buoy

Marks areas designated for swimming.

14. Spoil Ground Buoy

Marks areas where dredged material is deposited.

15. Keep Out/ No Anchoring Buoy

Prohibits anchoring in a specific area.

16. Controlled Area Buoy

Marks an area under control, such as for military operations.

17. Weather Reporting Buoy

Collects and transmits meteorological data.

18. Oceanographic Buoys

Collect and transmit data related to ocean conditions. These are also known as ODAS Markers or Ocean Data Acquisition Systems.

19. Wave Measurement Buoys

Also known as Wave Buoys, they monitor wave height and other wave characteristics.

20. Oil Spill Monitoring Buoys

They are used in areas prone to oil spills or other pollutants to track the movement and spread of oil spills.

21. Research Buoys

Support scientific research, collecting data on various marine parameters such as temperature, pH level, salinity, turbidity, etc.

A research buoy colored yellow with various instruments installed.
Image: NASA Stennis Space Center.

22. Ice Buoys

They are used to monitor and measure the movement and thickness of sea ice.

23. Regatta Buoys

Used in sailing and boating races to indicate the course and boundaries of a sailboat race. Also known as race buoys.

24. Mussel Farm Buoys

Indicate the location of cultivated mussels and other shellfish in the water

25. Naval Exercise Buoys

Mark areas used for military exercises.

26. Underwater Cable Buoys

Indicate the presence of underwater cables.

27. Fishery research buoys

Specialized buoys are used in the ocean to collect data on fish populations, water temperature, salinity, and other oceanographic parameters.

28. Drift Buoys or Drifting Buoys

Floating markers intentionally set adrift to follow the movement of ocean currents.

A Navy crew deploying a red Drift Buoy into the sea.
Image: US Navy.

29. Installation Buoys

Used to mark the location of offshore structures like oil rigs, wind farms, and subsea pipelines

30. Temporary Buoys

Deployed for short-term purposes, such as marking a temporary hazard or construction zone.

Buoys serve an invaluable purpose in the maritime world by providing visual markers for navigation, hazards, channels, and underwater infrastructure.

While most seafarers may only be familiar with the basic markers, there is an extensive range of buoy types, each with specialized roles and functions.

Identifying them is part of safe navigation and should be included in your voyage planning as practically as possible.

Knowing them may be helpful since most coastal shores are becoming more complicated. Besides, they should be of help in the decision-making process during navigation.

May the winds be in your favor.