There are 2 flags used in the world to indicate that divers are in the water. What is the difference between the two and when should each be used?


The A flag or Alfa (alpha) flag has a clear international meaning meaning: "I have a diver down; keep well clear at slow speed"


The red and white diving flag is a common sight in North America but is not commonly seen elsewhere. Its meaning is also less precise.

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From the Canadian Safe Boating Course required by all power boaters in Canada:

The international diving flag (usually blue and white in colour) must be displayed by any vessel engaged in diving. A red and white flag carried on a buoy is used to mark areas where diving is in progress, although divers may stray from the boundaries of the marked areas. The Code of signals Flag A is regulated under the Private Buoy Regulations. When encountered the operator of a pleasure craft must keep well clear at slow speed.

The Collision Regulations Rule 27, made under the Canada Shipping Act specifies that:

The dive boat must carry a rigid representation of the international code "A" flag not less than 1 metre (39.25") in height if the boat has divers down and cannot maneuver. Measures shall be taken to ensure all-round visibility.

At night, the boat shall display three all-round lights in a vertical line, the highest and lowest of which shall be red and the middle light shall be white. The red and white diver down flag is not recognized for use on the boat. There is no rule that forbids its use however.

A buoy may be used if it meets the specifications set out in the regulations. The Canadian Aids to Navigation (TP 968) recognizes the use of the red and white flag on a buoy, and the Private Buoy Regulations (SOR 99-335) provide the specifications for the buoy itself.

A diver"s buoy must be:

White, with yellow retro-reflective striping, a minimum of 15.25cm (6") across and 30.5cm (12") above the water, bearing the letters "PRIV" on opposite sides in large black lettering and displaying the owner"s name and contact information prominently. It must be flying the red and white diver down flag, which must be square and 50cm (20") on each side, with the white stripe extending diagonally from the tip of the hoist down to the bottom of the fly. The buoy must be securely moored.

There is no regulation saying how far a boat must stay away, OR how close a diver must stay near the flag/buoy/boat. The Safe Boating Guide issued by Transport Canada recommends boat operators keep clear 100m (328") from a diving flag/buoy


In practice, one is more likely to see a red and white flag than a blue and white flag for pleasure scuba divers in Canada and the US where it is widely recognized.

Photo By Soljaguar (Own work)


Commercial divers scuba and otherwise will usually have the international blue and white flag displayed. The commercial divers may or may not have the red and white flag displayed in addition to the International Dive Flag.

Photo By Marco Busdraghi (Own work) , via Wikimedia Commons

EIGHTH COAST GUARD DISTICTSPECIAL NOTICE TO MARINERSGULF OF MEXICO00-2008 document is quoted below and addresses the flag issue.

The US Department of Homeland Security special notice to mariners

The link is to a pdf document. The following paragraph is on page 23.


There has been some confusion over the status of the traditional sports divers" flag because of a change to theU.S. Inland Navigation Rules concerning the use of a one meter rigid replica of the International Code FlagAlpha (a blue and white flag). The Alpha flag is to be flown on small vessels engaged in diving operations whenever these vessels are restricted in their ability to maneuver if divers are attached to the vessel. But in sports diving, where divers are usually free swimming, the Alpha flag does not have to be shown and the Coast Guard encourages the continued use of the traditional sports diver flag. The distinction the CoastGuard wants to make clear is: The Alpha flag is a navigational signal intended to protect the vessel fromcollision. The sports diver flag is an unofficial signal that, through custom, has come to be used to protect thediver in the water. It is the responsibility of the operator of a diving vessel to determine if his craft"smovements are restricted. To be most effective, the sports diver flag should be exhibited on a float in thewater to mark the approximate location of the diver. NOTE: I have modified paragraph breaks and bold for emphasis. cd

The Red and White diver down flag has another meaning

The diver down flag has been adopted by dive supply shops and other suppliers as a sign that diving services or supplies are provided by the shop. It is flown on land with no diver in the water for that purpose.

History of the diver down flag.

designed and introduced in 1956 by Navy veteran Denzel James Dockery. After making a home made scuba gear he found he needed a way of keeping curious boaters away and designed the red and white divers down flag. For a history of the design here is a link to article.

The bottom line is a bit confused. The intent is not. Keeping boats and divers safe. So in North America where the red and white diving flag is recognized (and often required) it should be displayed prominently by all sports divers. Putting up the Alfa flag as well does no harm at all but will probably not be recognized by all boaters..

Elsewhere in the world the International Alfa flag is widely recognized and should be flown, it is usually the law to do so anyway. Adding the red and white flag does no harm and is not usually prohibited. If you are diving in a country where you are not familiar with the custom and law, ask a local dive shop. If in doubt fly both flags.

Commercial divers and deep sea divers with air hoses will display the alfa flag not only to warn of divers below but also to warn other vessels that the ship has restricted movements due to divers attached to air lines.

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This page is not intended to replace legal advice. This information is for general knowledge. I make mistakes. Laws and regulations change. I think I am current but this could change tomorrow. Use your head and do your research. Have fun too.