A diver down flag, or scuba flag, is a flag used on the water to indicate that there is a diver below. In North America it is conventionally red with a white stripe from the upper left corner to the lower right corner. Internationally, the code flag alfa/alpha, which is white and blue, is used to signal that the vessel has a diver down and other vessels should keep well clear at slow speed.
The purpose of the flags is to notify to any other boats to steer clear for the safety of the diver and to avert the possibility of a collision with the dive boat which may be unable to maneuver out of the way. The use of the red and white flag, which was designed and introduced in 1956 by Navy veteran Denzel James Dockery, is required by law or regulation in many US states and Canada, as well as in several other countries in the world. Usually the regulations require divers to display the flag and to stay within a specified distance of it when they are near the surface. As well there is often a larger zone around the flag where no boats are allowed to pass. Some states also prohibit the display of this flag when there is no diver in water. It can be placed on a boat or on a surface marker buoy. (from Wikipedia)
I found it fascinating to recently discover that my dad, through Seacraft Industries, had owned the Trademark for the diver’s flag as their logo. I always knew it was used on Seacraft products, catalogs and marketing materials, but had never thought about it. In the late 1950’s, they applied for and were awarded the right to use the diver’s flag as the registered trademark logo for Seacraft Industries and their products. He did not design or hold the patent to the flag, but when he researched the Trademark and found it was not owned by anyone, he applied for and got it. He said it took three years to go through the process and he still has all the original paperwork, which I’ll get my hands on one day soon for the family history archives. In the meantime, this is a Boston Herald article about it and a copy of the cover of the 1962 catalog, possibly the same one King Hussein of Jordan had placed his order from. https://goodmorninggloucester.wordpress.com/2014/01/29/obscure-bit-of-interesting-stuff/