All right already you guys. Let's help this lad out...
That is, assuming that you, ds797, are indeed a lad. There's nothing to go on from your profile. Nor do you clue us in to where you live or might want to travel to.
Public nude swimming used to be par for the course here in the U.S., when schools were separated by gender and large enough to have their own pools. Most YMCA's had nude swimming in the past. Mine did. Lots of history on that is available. And in many places around the world nude swimming at public baths, pools and even parks were and are a common thing. Some with boys only days and girls only days. I figure this may be long gone for the most part now, other than in private clubs and beaches and parks that are are designated as clothing optional. But, all that doesn't help you out...
I'd suggest going to a local liberal or gay bookstore and looking through the many guides to nude beaches, hot springs, swimming holes, etc. I don't know if you are a gay man or not, ahem, no matter; any gay guide worth it's salt will have information on where to find safe places to be nude, (and perhaps not so safe places, that may turn out to be quite an adventure). Also, look for The Rough Guides, also published as The Real Guides. I've found them to be a great source of information on local places to swim, nude or not.
Other than very family oriented private nudist swimming clubs on the West Coast, the last nude pools I went to were in London. That was in 1996, so who knows now. These were listed as Public Baths in the guides. One in particular was a really great experience, in more ways than one. I don't remember it's name, and I don't have my books handy, but I think it was in the East End somewhere (???). Seek and ye shall find. I hear and read about many places in Germany, Scandinavia and Eastern Europe. Cuba still has several of it's original YMCA buildings and I would not be surprised that nudity is allowed there. Anyone here know?
Every once in a while I'll hear from someone that the YMCA in blah-blah Iowa or blah-blah Kentucky, still has nude swimming days. So keep asking around. (The men's only Y next door to the Naval base in Bremerton, WA, did until the late 80's...it was HOT). Even here in prudish Seattle there are three well known, although illegal, nude beaches. Everyone just watches out for the cops.
Since you are new here, try searching the Forums for nude beaches, etc. There's bound to be some helpful threads that come up.
For better assistance in the Forum you should let us what part of the world you are curious about so that we can narrow down our information for you.
You could even Google it. Be specific, ds797. -Steve