Diver Down Flag

The Diver Down Flag, also known as the Alpha Flag or Code Flag 'A', is a crucial international maritime signal flag. It is not a national or territorial banner but a safety and warning signal used globally on the water. The flag features a simple yet highly visible design: a white rectangular field with a blue swallowtail and a prominent white stripe running diagonally from the top hoist to the bottom fly.

Its primary function is to communicate that a vessel has divers in the water nearby and that other boats should maintain a safe distance and proceed at a slow speed. This flag is recognized under the International Code of Signals and various national boating regulations. The distinctive swallowtail shape and contrasting colors are designed for maximum visibility against water and sky, ensuring the message is understood even from a distance.

While often used recreationally, the display of this flag carries legal weight in many jurisdictions, where ignoring its warning can result in penalties. It is a critical component of dive boat operations and is frequently flown in conjunction with the red-and-white diver down flag used primarily in the United States and Canada.

The flag's design is purely functional, with each element serving a clear safety purpose. The blue and white color scheme provides high contrast for visibility. The blue swallowtail on a white field is the specific pattern for the letter 'A' (Alpha) in the international maritime signal code, which means 'I have a diver down; keep well clear at slow speed.'

The diagonal white stripe cutting across the blue further enhances the flag's distinctiveness, ensuring it is not mistaken for other solid-colored or simple two-color flags. There is no symbolic or historical meaning attached to the colors beyond their practical utility for communication and safety. The entire design is a standardized signal, where the shape and pattern are the message itself.

The flag's origin is tied directly to the establishment of the International Code of Signals. The current design for Code Flag 'A' was formally adopted with the revision of the code. Its use specifically to indicate divers in the water became standardized in the latter half of the 20th century as recreational scuba diving grew in popularity, creating a need for a clear, universal warning signal.

National maritime authorities, such as the International Maritime Organization (IMO), endorse its use. The flag's design and meaning are codified in international agreements and are included in official publications like the International Code of Signals and various national boating safety guides, giving it a firm legal and operational basis worldwide.