Interesting. I generally think of cock rings as things that enhance an erection but if you are referring to the less restrictive, decorative type that enhances the look of a flaccid penis then there's no legal problem wearing one to a nudist beach, but I'll get back to the appropriateness issue later.

Whether it's a good idea or not will also depend on the type of nudist beach you frequent. Some beaches are shared by families and I can just imagine the various questions parents would have to field if children should happen to see you walking around with a willy bangle. It's not obscene but how do you tell kids that they can't have one too, no matter how cool it may look?

Even at a beach that is primarily for textile-hating adults, I'd opt for rings that aren't too obvious. Perhaps more discreet ones that look quite sexy because you only get a glimpse of it as you saunter past. At the end of the day, cock rings have a 'Look At Me' factor to them and you may as well have a giant red arrow pointing downwards on your stomach if that's the statement you want to make by wearing a big cock ring. I don't think that's inappropriate but it depends on the message you want to convey to your fellow beach lovers.