September 22, a historical day for diving

[Akimbo]

... I understand why there was a need a need to distinguish between commercial underwater work and recreational divers. Thus the red/white in California and then the rest of the USA. Why did the rest of the world stay with the blue/white? Is there another flag that indicates UW operations in the US?...

I think it is fair to say that it is pretty complicated. Getting all maritime nations to agree on anything isn't easy. If I remember Navy boot camp correctly, signal flags can also be used in combination for a different meaning than when used alone. As I understand it, the world's navies developed the flag system before the days of the "Marconi" (radio) to coordinate ship movement. It continued to be used to maintain radio silence and because the early radios were less than reliable.

@Bob DBF can probably explain it a lot better, he was on the bridge in the blue-water black-shoe Navy... and correct me where I'm off in the weeds. Meanwhile, this might help: U.S. Navy Signal Flags

Edit:

Do commercial diving ops have another flag?

It isn't so much that commercial and military diving needs a separate flag rather than the red & white flag isn't an official international maritime standard and the Alfa flag also communicates restricted ship movement.

 

[Sam Miller III]

The red and white dive flag was originally proposed by the late Ted Nixon via SDM in 1957 .....After much discussion and many submissions of other designs the small dive community at that time settled on the red and white flag --Original Blaze orange --but later changed to red.

The blue and white flag was never discussed during the development of the red and white flag.

Remember the dive community at that time was in its formulation stage and very small and communication was via letter or telephone... As one manufacture stated at that time "The dart board industry is three tines larger that the dive industry ," Hopefully that places the diving of 1957 in perspective for you.

@Akimbo knows a heck of a lot more about he blue and white flag. Maybe he can add some history-- spent my service obligation as a Captain in the USAF during Korean war-- I came in on a crash landing at a naval base -- that was the sum total of my USN contact

Sam Miller, 111

 

[Akimbo]

I'm not sure if this is still the case but the Alfa flag was also flown by cable and pipe laying vessels when I was active offshore. This rule applies:

Rule 27 -- Vessels Not Under Command or Restricted in Their Ability to Maneuver

BTW: The Alfa flag is also known as the "A" flag or Code flag "A".

Just to be clear, the Alfa flag is on the left​

As I understand it, technically the Alfa flag should not be displayed while underway/not conducting diving operations. Painting it on the side of dive boats (recreational, commercial DSVs, or military) sort of confuses and defeats the purpose. The Diver-Down red & white also serves as a symbol for the recreational diving industry so less of a problem, IMHO.

 

[Bob DBF]

Lucky for me, @Akimbo, I escaped to the Submarine Navy with only a year on the surface.

Modern naval code signalling began with the invention of maritime signal flags in the mid-17th century by the Duke of York who was created Lord High Admiral. Before this ships used semaphore which was short range due to the size of the flags, or a cobbled togather arrangements depending on what signal flags the vessels in the group happened to have. The Admiral standardized the flags, meanings, and requirements to have proper complement of flags on a vessel.

If you go aboard a museum ship, ask the docent to see the signal bridge. There are racks where the flags were stored and could be raised faster than you can read this.

Signal flags are interesting in that it is a mater of context, in that there is the plain language shown by your link, which is in general maritime usage. The Navy can decide for a particular time, operation, or by flying another indicator flag, a flag can have a different (code) meaning altogether.



Bob