Alpha (A)
maritime signalsmaritimesignal flagnavigation
The Alpha flag is a white and blue swallowtail pennant, flown to indicate a diver is below the surface. When displayed, all nearby vessels must keep well clear and reduce speed to avoid creating dangerous wake or currents. It is one of the most commonly recognized signal flags in harbors and dive sites worldwide.
Despite the Alpha flag being the international standard for indicating diving operations, many recreational divers use a red flag with a white diagonal stripe instead, which is actually only officially recognized in North America and a few other regions.
Adopted: 1857
