Knavey once bubbled...
Has anyone ever had something stolen from a fellow diver? There is always the possiblity that the person doing the stealing is someone who knows EXACTLY what that dive flag means. Hate to bring this up, but its probably true.
In the better than twelve years I've been diving, I have never had any gear stolen at any time with the possible exception of a dive knife while in Roatan and that could well have simply been lost. Gear laying around on picnic tables at training areas, boats and so on it typical and by-and-large I have found divers to be trustworthy. Perhaps because they respect what it costs to buy that gear... or maybe because I'm an instructor and they look at my stuff and think "that junk's way too worn out to be worth stealing" ~grin~
Seriously though... for example, this past weekend, I had a group of five students at Devil's Den -- as is standard practice we left our gear and such at the picnic tables when diving. We would be gone for an hour at a time and everything was always right where it was left when we returned. I find that to pretty much always be the case.