Very, very gradually, society seems to be becoming more tolerant of more of the body being visible in public, although it's still a long way from it being OK to pop out to put the rubbish bins out without having to put something on first.
One of the more obvious advantages is comfort... that when it's hot, not having anything against your skin is very comfortable.
It's practical, too, if you tend not to wear anything at home, and want to pop out for something that won't take long (putting the rubbish out, posting a letter, etc). Even better would be a society in which you also had no need to lock the door on popping out! (Another Eden concept!)
Naturists are generally more friendly and relaxed together than the English general public. This is one of three such groupings of people I've found so far, the others being bell-ringers and Land-Rover owners.
Another great plus is that it's harder to indicate status and push a particular constructed image when not wearing anything. When people wish to get people to believe something about themselves that isn't really the case, or to distort the truth by over-emphasizing something, one of the steps they take is to dress appropriately for that rôle. (Some people go in for tattoos and / or piercings in a big way, though.)
I've known someone who felt bad about her body after having been abused as a child recover almost completely from that after going to a naturist swim -- she was once again able to feel that her body wasn't something bad. That's a particularly strongly contrasting form of finding freedom, but it's part of a more general effect... it's great to see people discovering that being completely exposed is perfectly safe.
There is, to me, something more beautiful about human body itself than there is about coverings we make for it -- the phrase "gilding the lily", comes to mind.
One thing that people worry about with the prospect of social nudity is that of gawkers... inadequate individuals who want to use people so they can feel alright about themselves. One way they can do this is by seeing people naked... I think the way this works is that they understand someone letting someone see them undressed as being a sign of proferring intimacy, and they feel they lack that intimacy, but by creating a copy of an effect of being accepted, they try to make themselves feel that the underlying cause of that effect is there -- this is not the only form of this, buttonholing people into conversations so the buttonholer can try to hide from the fact that their company is unwanted is another, also very annoying, one. Frottage -- brushing against people without their wanting contact, as a way of getting some contact -- is another. What are the solutions to these problems? Well, letting them gawk, buttonhole, and frot isn't really helping them... perhaps talking to them about their inadequacy and pointing out that they need to get a life of their own and that no-one can do it for them, is more of a real solution, although it's not always regarded as socially acceptable..
Sometimes people worry that public nudity will lead people astray morally, but this is a load of rubbish -- social nudity is not sexual, and the way people dress to project particular images is much more likely to lead people astray! Also, although I'm happy to say one shouldn't encourage anyone's tendency to stray from what is right (and finding what is right is the subject for at least one more essay!), it must be remembered that the tendency to stray is in the one who strays.
Some people expect that they'll feel embarrassed about people seeing them naked, but this disappears very quickly on trying it! Of course, it helps if most people in the situation are also nude. And some are embarrassed at the prospect of seeing others naked -- but in fact everyone's so casual about it in practice that one soon stops being specifically aware that people aren't wearing anything.
Were society in general to go over to regarding clothing as optional, there could be problems while people get used to it, but as far as I can tell the time taken to adjust really isn't long at all.
In many parks in Germany, nude sunbathing is publicly acceptable, and there are now suggestions for campaigning for such tolerance in the UK. This seems healthier to me than setting aside some beaches as nudist beaches.