I love skinny-dipping too. I think in 'older times' here in the USA (the 1800's, and before, for example) people routinely skinny-dipped because bathing suits would have been prohibitively expensive to most people at the time. I wonder why the convention came around that suits were 'normal'? No other mammal dons clothes to get totally wet
Anyway - I would hike back to the small creek near our family farm when I was younger - usually I was just wading in the creek but one time I went back there & stripped & swam for a couple hours. It is very very freeing and great to be at one with nature. I admit, the rush of doing something that I thought others would think of as 'bad' made me aroused, and I did get out of the water, hard, layed down on an area of sand and covered myself up in it. I layed there in the bright sunlight, but the erection would not abate so I - um - took care of that
It was nice - just being there totally alone (there was no one around for miles).
My other experiences skinny dipping were in our own backyard pool - often very late at night. This was totally relaxing & sensual but NOT sexual. As others have said it just feels good to have the freedom, I guess. You never realize how restrictive bathing suits are until you're without one in the water....
DP