The Ultimate Guide to Buoys and Flags

Boating navigation is no different from driving cars. Just as we have road signs and traffic lights that we strictly follow on land, there are also internationally recognized signs and signals, in the form of buoys, marks and flags that prevent us from damaging our vessels, and worse, putting ourselves in danger on the water.

To be more familiar with these, we have included in this article an introduction to the systems of navigation as well as images, purposes, and descriptions of buoys and marks. We also have a 2-page PDF that you can download and print for free, so you can have a hand-carry guide when you finally start your journey! Nautical flags and the International Code of Signals are also discussed thoroughly.

Systems of Navigation

Until the 70s, there was no single authority that implemented rules of navigating maritime waters, which caused confusions and lots of accidents, and only in the 80s that the International Marine Aids to Navigation and Lighthouse Authorities or IALA was established. Currently, there are two systems used by boaters around the world, the IALA Region A, that is being used in Africa, most of Asia, Australia, Europe and India, and the IALA Region B, in North, Central and South America, Japan, Korea and the Philippines.

There are very few differences between the two systems, in fact, they are almost identical, except that IALA Region A port (left) lateral marks and lights are colored red and starboard (right) lateral marks and lights are colored green, while it’s the opposite in IALA Region B.

Definition of Terms

Port – Left side of the boat

Starboard – Right side of the boat

Channel – Body of water between two close landmasses, e.g. river, strait, harbor

Fairway – Navigational area of a channel

Bifurcation – Point where at which a channel branches into two

Buoy – floating navigation aid in the water

Marks – fixed navigation aid in the water

Mooring – Point of anchorage

Light Flashing – Series of light flickers with different meaning

Marks vs. Buoys

Marks and buoys are navigational aids in the water that come in different colors, shapes, and markings, used to help boaters in choosing which direction to go and areas to avoid, or to provide important information to ensure everyone’s safety in the area, whether on board or not.

Marks are fixed aids usually on poles and pilings while buoys are floating aids that are anchored to the bottom. In areas where it’s shallow enough to drive a piling, marks are usually preferred as they do not require as much regular maintenance. On the other hand, in deep waters where it’s difficult to drive a piling, putting a buoy makes more sense. Also, in places where channels may shift and change over time, placing a buoy that is movable and can be anchored is the more common practice.

Lateral Buoys/Marks

Lateral buoys/marks indicate which side of the buoy is the safest to follow when in a channel. There are four kinds of lateral buoys that differ in color, namely port hand, starboard hand, port bifurcation, and starboard bifurcation.

Lateral Buoy	Port Hand Buoy/Mark	Starboard Hand Buoy/Mark	Port Bifurcation Buoy/Mark	Starboard Bifurcation Buoy/Mark
Meaning	Marks out the port side of passage way or channel	Marks out the starboard of passage way or channel	Marks where channel splits and to proceed with the channel on the right	Marks where channel splits and to proceed with the channel on the left
Keep on this side of the boat	Left if traveling upstream	Right if traveling upstream	Left if traveling upstream	Right if traveling upstream
Color	Green; Retroreflective	Red; Retroreflective	Green with single red horizontal band; Retroreflective	Red with single green horizontal band; Retroreflective
Body Shape	Cylinder, pillar or spar	Cylinder, pillar or spar	Cylinder, pillar or spar	Cylinder, pillar or spar
Top Mark	Single green cylinder	Single red cone pointing upward	Single green cylinder	Single red cone pointing upward
Light Color	Green	Red	Green	Red
Light Rhythm	Flashing or quick	Flashing or quick	Group flash (6s or 10s)	Group flash (6s or 10s)
Markings	odd numbers	even numbers	letters	letters

For a clearer visualization of buoys and marks in the channel, here is a map that shows where they will be located while traveling upstream.

Cardinal Buoys

Cardinal buoys also mark which side of the buoy is safe to travel, however, instead of going left and right, they tell us whether to go north, south, east or west. Similar to lateral buoys, they are pillar or spar shaped. They are black and yellow in color and sometimes equipped with white light.

Special Buoys

Special buoys mark an area for a specific purpose. They usually have no designated shape and with yellow light when equipped. Some special buoys are not labelled, while some are, and if it is, the mark is never a number.

	Anchorage	Cautionary
Meaning	Marks a designated area where you can anchor your boat	Marks a danger and general boating is not permitted could be underwater pipeline, a firing range or seaplane base
Color	Yellow; retroreflective	Yellow; retroreflective
Body Shape	Cylinder, pillar or spar	Cylinder, pillar or spar
Top Mark	Cross if present	Cross if present
Light	Yellow on any rhythm not used for white light	Yellow on any rhythm not used for white light
Marking	With anchor symbol on the body	Marked with letters on the body if present

	Control	Hazard	Information	No Trespass
Meaning	Notes speed limits, wash restrictions, and other limitations	Notes a hazard such as a shoal or a rock that are usually in the middle of or surrounded by navigational waters	Share local information like campsite, marina, etc.	Designates area where boats area that prohibits entry
Body color	White with limitation indicated in orange circle in between two orange bars	White with orange diamond in between two orange bars	White with orange square in between two orange bars	White with orange diamond with cross at the middle in between two orange bars
Shape	Mostly cylinder	Mostly cylinder	Mostly cylinder	Mostly cylinder
Light color	Yellow when equipped	Yellow when equipped	Yellow when equipped	Yellow when equipped
Light Rhythm	Any rhythm not used for white light	Any rhythm not used for white light	Any rhythm not used for white light	Any rhythm not used for white light
Markings	With restrictions/limits information inside the orange circle	Danger can be pointed out inside the orange diamond	Information inside the orange square	none

	Diving	Mooring	Scientific/ Ocean Data Acquisition System (ODAS)	Swimming buoy
Meaning	Marks location where diving occurs and boaters should steer clear the area to avoid accidents	Notes place where boats may tie off to dock, other boats may be in the area so speed limit should be reduced	Buoys that record data such as weather, water temperature, currents, etc. therefore should keep distance from this buoy	Marks a swimming area and boats are not permitted to enter
Color	Any	Typically white with orange cap on the top	Yellow	White
Shape	Any	Any	Any	Mostly cylindrical tied on a rope
Top Mark	Red flag with white diagonal stripe	Usually has a sphere top mark	None	None
Light	None	None	Yellow when equipped; flashes 5 times in 25 seconds	None

Nautical Flags

Even though we already have radio and other electronic devices available to easily communicate with other boaters, a lot still use nautical flags. The reason being that they are cheap and very reliable as they do not need power to be operated.

These are colorful flags that are used to signal other boaters just like our head and rear lights when we want to turn or change lanes on the road. However, reading nautical flags can be very confusing at the beginning as there are a lot of flags each corresponding to a letter and a specific meaning, compared to just left and right in cars.

How to Read Nautical Flags

The easiest way to read nautical flags is to look closely on their designs and meanings. Remember that nautical flags only use five colors: black, blue, red, white, and yellow. Shapes are very important as well, square/rectangular flags are used for letters, while pennant flags (triangular with flat tip) are numbers.

Below are the square flags, alphabets they represent and what they mean.

Flag	Name	Letter	Meaning
	Alpha	A	Keep clear, diver is down.
	Beta	B	With dangerous cargo.
	Charlie	C	Yes.
	Delta	D	Keep clear, trying to move.
	Echo	E	Changing course to starboard.
	Foxtrot	F	I am disabled.
	Golf	G	Seeking a pilot.
	Hotel	H	Pilot on board.
	India	I	Changing course to port.
	Juliet	J	Burning vessel, keep away.
	Kilo	K	Need to communicate with you.
	Lima	L	Stop vessel immediately.
	Mike	M	Vessel is stopped.

Flag	Name	Letter	Meaning
	November	N	No.
	Oscar	O	Man overboard/out.
	Papa	P	Vessel about to sail.
	Quebec	Q	Permission to pass through.
	Romeo	R	Turn back.
	Sierra	S	Engines going astern.
	Tango	T	Stay away.
	Uniform	U	Approaching danger zone.
	Victor	V	Need help.
	Whiskey	W	Need medical attention.
	X-Ray	X	Stop what you’re doing.
	Yankee	Y	I am dragging my anchor.
	Zebra	Z	Need a pull.

Numbers in Flags

There are 10 flags that represent numbers. Two or more digit numbers can be represented by combining these flags.

Flag	Number
	1
	2
	3
	4
	5

Flag	Number
	6
	7
	8
	9
	0

Flying the Flags

Aside from each flag’s meaning discussed above, boats can fly combinations of flags up to seven flags in a row, which will then mean differently.

For example, if you see a solo D (Delta) flag, this means “keep clear, trying to move” and a solo V (Victor) flag, this means “need help.” However, the combination of D (Delta) and V (Victor) flags, will mean “I’m maneuvering with difficulty and require assistance.” Another, a solo J (Juliet) meaning “burning vessel, keep away” and q solo L (Lima) meaning “stop vessel immediately.” Together, these flags mean “you’re running the risk of going aground.”

As a general rule, signals with two nautical flags mean some type of distress or maneuvering issue. Three or more flags can include pennants and denote things like points of the compass, geographical signals, names of ships, time and position, as well as latitude and longitude.

Buoys and nautical flags can be really overwhelming at the beginning, that’s why we have prepared a 2-page PDF that you can download here and print to have a cheat sheet while on the water! With more opportunities of sailing and seeing these buoys and flags, you will surely be familiar with them in no time!

Also, if you find this article useful, please let us know by commenting below!