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Diver down signal flag

image by Alexander Voscorian, 26 May 1998

About the flag
Differences between ICS Alfa and Diver Down

See also:

About the flag

Red, with a white stripe from upper hoist to lower fly. Usually square. This is the “diver down” flag, flown from a ship to indicate that there is a diver below. Also flown by (and for) diving enthusiasts.
Steve Kramer, 24 Apr 1998

The red and white diver-down flag, originally devised in about 1957, is intended to protect divers themselves. This flag is often referred to as unofficial or voluntary because it is not mandated by the international or inland rules of the road. This assertion is erroneous.
Joe McMillan, 17 Jun 2005

This is to notify any ships (or boats) to steer clear for the safety of the diver.
Bill Grimes-Wyatt, 04 Apr 1997

Known as the skin diver flag. It represents a “diver down”. Though I’m not a skin diver, I believe that this flag is flown when a diver is in the area of the boat in order to warn other ships away. The underlying premise, the safety of the diver, is obvious.
Paige Herring, 05 May 1998

This is the flag indicating that there is a diver below water. I believe that it is an internationally recognized symbol. The flag is supposed to fly above a bouy that is anchored (to the bottom or to a sea anchor) in the area of the diver’s work. Theoretically, the diver may surface near that buoy / flag and not be in danger of being struck by boats.
Nick Artimovich, 31 Mar 1997

I believe the international symbol is the "A" letter flag.
Nathan Bliss, 31 Mar 1997

Extended use

I see it often on car windows, bumpers, etc., and it is always on a vehicle of someone who is an avid diver.
Rob Raeside, 31 Mar 1997

In the U.S. it is is more often seen flying from stores selling or renting diving equipment, which is a “violation” of the flag’s intention (unless, of course, the basement of the store is flooded and a diver is at work below.)
Nick Artimovich, 31 Mar 1997

It is also often seen at scuba service stations and on cars of scuba enthusiasts.
Nathan Bliss, 31 Mar 1997

It is often used by scuba divers as a bumper sticker, etc to inform others of their interests.
Bill Grimes-Wyatt, 04 Apr 1997

This flag is also used as cover art for the Van Halen album Diver Down.
Josh Fruhlinger, 31 Mar 1997

Differences between ICS Alfa and Diver Down

Two flags are mandated for display in (at least) most parts of the United States and Canada when a boat or ship has divers in the water. Considerable confusion exists as to the differences between these two flags, if any, and why a dive boat has to use two separate signals. In fact, the two flags serve quite different purposes.

The 1972 International Regulations for Preventing Collisions at Sea, as well as national legal instruments, such as the United States Inland Navigation Rules, provide for an elaborate series of day-shapes and lights to be displayed by large vessels whose maneuverability is restricted by the conduct of underwater operations, such as cable-laying, dredging, or conducting diving operations. Smaller vessels that are not able to hoist the complex signals used by large ships are instead required to display a rigid version of the International Code of Signals flag for the letter "A", known as ALFA, at least one meter high if diving operations restrict their ability to maneuver. Not all boats from which divers are swimming are necessarily so restricted. Generally, only vessels to which the divers are physically connected by communication lines, air hoses, or the like are affected by this requirement. It does not apply to most instances of sport diving, where the divers are swimming free of the vessel. As recent U.S. Coast Guard Notices to Mariners emphasize:

The ALFA flag is a navigational signal intended to protect the vessel from collision.

The use of the diver down flag is required by state law or regulation in virtually every state of the U.S., as well as by various U.S. Federal agencies exercising jurisdiction over waters where diving takes place (such as the U.S. National Park Service), by the Canadian Occupational Safety and Health Regulation and in many other countries. Typically, the laws or regulations on the use of this flag require divers to display the flag and to remain within a specified distance of it when they are near the surface. This often means the flag is best mounted on a float or buoy near the actual dive point rather than on the boat itself. Restrictions vary from state to state, but typically include a zone around the flag where no other boats are allowed and a second, larger zone in which their speed is limited. A number of states also prohibit the display of the diver-down flag when a diver is not actually in the water.

Joe McMillan, 17 Jun 2005