On a vaguely related note, I've been thinking back to my school days: I once went skinny dipping, although it wasn't entirely intentional.
Nowadays CH has a deluxe sports centre, but when I first went there (in 1985) the swimming pool was a bit more basic. There was an old (empty) diving pool, and then the main pool that everyone used. This pool had cubicles along the sides with plastic curtains, a bit like the changing areas you find in some shops, and this was where the boys got changed; the girls had a separate changing room.
Anyway, this arrangement did lend itself to a prank at the end of a session: if people timed it right, they could pull back the curtain just after someone had taken his swimming trunks off, then throw him into the pool. This happened to a few people, and one day it happened to me. (I should clarify that this was all good natured, rather than a form of bullying.) A couple of boys grabbed me by both arms, and initially I pulled back, trying to stay inside the cubicle. However, I recognised that they'd eventually win so I decided that it was better to just accept it rather than being dragged out slowly, and I was basically catapulted into the pool. The pool was empty at this point, and the next group of people were sitting at the far end (including girls), but I think they were too far away to see any details, particularly since I was moving quite quickly. The other boys handed me my towel as I climbed back out, so I was able to avoid exposing myself.
The interesting thing is what happened in between, when I was submerged. I wouldn't quite describe it as "liberating", but that's probably the word that comes closest. It may be significant that I was thrown in (rather than climbing in), so the transition was quite abrupt. More importantly, this meant that I sunk a long way before I floated back to the surface; as I recall, the deep end of that pool was 3m. I went in feet first, so I was basically upright, and I was able to stretch out my arms and legs in all directions without breaking the surface or touching the walls/floor of the pool.
It may be easiest to describe this by comparison to similar events. If I'm taking a shower then I'm naked, but the water is a spray that only hits certain points of my body at any one time. In a bath, I may be able to get completely submerged, but I have to squash myself into a position where my arms and legs are jammed against the sides. If I'm swimming then I can spread out a bit, and I do get wet everywhere at once; swimsuits aren't exactly waterproof! However, the presence of the swimsuit does distract from the feeling of the water. It's not just the swimsuit; the same thing applies to goggles or a watch. (When I was at school I used to wear my watch at night, and I felt naked without it if I lent it to someone else, even when I was wearing pyjamas.)
I think the key aspect of this is sensory input. I kept my eyes closed (due to the lack of goggles), and it was pretty quiet underwater (especially because I was the only one in the pool). I obviously couldn't smell anything (anosmia), and I kept my mouth shut so I wouldn't have tasted much. That only leaves my sense of touch, and I was getting the same feeling from all of my skin, with nothing to distract from it.
Something similar happened when I did my first parachute jump in Durham: the thing that most surprised me during freefall was the silence. There are lots of background noises that you just get used to, and it's only when they're gone that you can really appreciate the calm.
There was an episode of Baywatch Hawaii ("Shark Island") where one of the lifeguards (Jesse) tries swimming naked in the sea. She's initially a bit dubious about it, but then finds that it's better than expected; I think the episode handled it pretty well. It's not a sex thing (particularly if you're alone), it's more of a hippie thing, being "at one with the water".
All in all, I think it's a worthwhile experience. I haven't repeated it (mainly because it would break the dress code in most pools), but I'd certainly recommend trying it if you get the chance.
And finally, I do like this Bud Light advert from a few years ago.