Have you ever wondered how that red and white flag familiar to all divers came to be? As most know, flags are used in maritime operations as signals to communicate with other vessels. The International Signal Flag "A" (Alpha) is used by vessels to signal the danger of collision to other vessels in the area. More specifically to diving, the alpha flag is used to communicate "I have a diver down, keep well clear at slow speed". This flag is more commonly used in Europe and the British Commonwealth, including the UK, Ireland, Australia, Canada, New Zealand, South Africa and Kenya, as well as the Russian Navy, even though you may see it used on U.S. vessels. Generally this flag is used in situations where the diver is physically connected by means of life support or other system to the vessel itself.
But that doesn't answer how the red flag with the white diagonal stripe came to be. Back in the 40's the solid red "Baker" flag (later called the "Bravo" flag) was used by the U.S. Navy to signal DANGER a diver at work in the water nearby. In 1949, Denzel James Dockery, a Navy diver, was discharged from his military service. A tinkerer at heart, and eager to use the skills he trained for in the Navy, Denzel "Doc" Dockery followed instructions he found in a 1953 Popular Science magazine to build his own SCUBA unit.
While trying to make a living in Michigan with his scuba skills, "Doc" found that civilian marine operators did not recognize or acknowledge his use of the "Baker" flag to signal he was in the water. Working with his wife, Ruth, they tried to design a flag that would catch mariners attention. At first they designed a red flag with a horizontal white stripe across the middle, but it soon came to their attention that this was the national flag of Austria. They thought of using a red flag with a vertical white stripe, but this was a Navy numerical signal flag for the number 7. So after further research they arrived at the unique design you see today of the red flag with then diagonal stripe from the upper left to the lower right.
"Doc" began using this flag while he worked and promoting its use through the local dive club "Cuadro Pescadores" to which he belonged. In the early 50's the Dockerys opened a small scuba shop in Flint, Michigan, and sold the flag from their shop. In 1956, a U.S. Divers sales rep, Ted Nixon, came into the shop and offered to sell the flag nationally as he made calls to his other shops. (Thanks to his widespread efforts to adopt this flag, Nixon is often mistakenly credited with the creation of the flag.) In the meantime, "Doc" and his fellow club members worked to get the Michigan State Legislature to recognize the flag as a means by which to protect SCUBA divers from marine traffic.
Another boost to the recognition of Dockery's flag came when it was mentioned in a September 1957 Skin Diver magazine article asking readers what they thought of the flag and if they had any other ideas. In February 1958, readers chose Doc's flag as their symbol of choice for a dive flag. In the meantime the newly formed Great Lakes Diving Council was also promoting the use of the flag to legislators in Ohio, Indiana and Illinois.
Thanks to the innovation and determination of Denzel and Ruth Dockery, the diver-down flag is recognized by the U.S. Federal Government and most of the states as the official warning sign for a diver's safety.