HomeA-Z ScubaEquipmentAccessories › Flag

Diver Down Flags Explained

Divers float coloured flags at the surface of the water to alert boat traffic about their presence below and they may soon be making an ascent.

This guide explains how to use the red and white "diver down" and the blue and white "alpha flag" to warn boaters that scuba divers are in the area.

What is the Purpose of Floating a Dive Flag?

The main reason for using one of the recognised scuba flags is to signal that people are below the water or close by, such as:

In fact, flying a dive flag is a legal requirement for divers in some areas - and one of the general scuba diving safety rules and regulations.

You learn why dive boats fly the diver down flag in the PADI Boat Diver course. The purpose is to show other watercraft that divers are in the water.

One simple solution is to attach a flag to an inflatable buoy that will float at the surface. Some divers will use a line and reel to tow it while they're in the water.

Key Features of Dive Flags

Pro Tip: Divers can use a wire frame stiffener to open up the dive flag and make it more visible. Modern inflatable tube styles provide excellent buoyancy and they have a pouch to store dive gadgets and gizmos (e.g. equipment for spearfishing, or your personal locator beacon).

How to Use Dive Flags

The flag must either be the red-and-white "diver down", the blue-and-white "Alpha", or both, as required by local regulations. Dive flags should be flown stiff and unfurled (open to the wind) and in good condition.


Dive Flag and Float | How to Use Flags for Scuba Diver SafetyThe flag with a red background and a white diagonal stripe signals that divers are in the water.

Float it at the surface from an inflatable buoy if you are unable to fly it from the highest point of a vessel.

The 'diver down' flag should be a minimum of fifty (50) centimetres (20") by sixty (60) centimetres (24") when flown from a vessel. It should be at least thirty (30) by thirty (30) centimetres when displaying the flag from a buoy.


The Alpha "A" flag is recognised internationally when flown from a vessel. It indicates that the vessel has restricted mobility in the water. Thus, other vessels should yield the right of way.


Scuba divers use a surface marker buoy (SMB) to alert boat traffic that they are making their ascent. Plus, audible signaling devices (e.g. a dive light, air horn, mirror, or whistle), will also help to get you noticed and heard by the surface support team (e.g. boat crew).

Pro Tip: The Drift Diving certification warns scuba divers not to assume that all boaters follow local laws. In fact, some boat captains don't even recognise scuba flags. Thus, if you hear a boat, stay down until it leaves the area before you come up - and stay close to your marker. You can report a diving incident online to the Divers Alert Network (DAN).


The ideal way to prevent diving injuries (and death from propeller strikes), is to make divers and boaters aware of one another.

Boat operators should stay a safe distance from flags used by divers. The drivers should keep a distance of at least ninety (90) metres (300 feet) from diver down flags and buoys in the open water. This minimum distance reduces to thirty (30) metres (100 feet) in navigation channels or inlets.

Here's the thing:

Divers should use diver down and Alpha flags in an appropriate manner. Divers should stay within ninety metres of the diver down flag or buoy in open water and aim to surface within forty five (45) metres (150 feet) of the flag.

Responsibilities for Divers

There are several ways to enhance diver safety in water. Besides making sure you're visible, you must also comply with any regional laws and restrictions.

Have a plan for making an appropriate response for a diver injured by a boat strike or by propeller blades. If there is an incident, follow the guidance on the DAN Emergency Action Plan template for evacuation procedures.

Responsibilities for Boat Drivers

Some of the recent scuba diving accidents and incidents show that boat operator inexperience and negligence are contributing factors.

As a boat operator, you should be constantly looking for people in the water. Being attentive and alert are effective ways to prevent severe boating accidents.

Pro Tip: Remember to rinse the gear in fresh water after use and keep it stored in a dry place (away from direct sunlight). General maintenance also includes checking the line for any worn or damaged spots - and replace them when it becomes necessary.

Divers also enjoyed reading about...