Rediscovering skinny dipping in the Lakes, which we used to do with family on holiday walks here and Wales, was the beginning of my path into naturism. I used to spend the summer mostly encased in wetsuits sailing and so would winter walk, so didn't get much chance, but I remember a couple of times on walks with my brother going in mountain pools, the second time introducing his children to it, but he wouldn't join in that time. As I sailed less in summer I started walking more, and so naturally more opportunity.
3 or 4 years ago I started doing a lot more 'wild swimming' and on a few occasions joined some of the many groups now doing it, but they mostly swim in wetsuits and I prefer a peaceful meditative swim au naturel. I did join one small group for a weekend camp in Eskdale and, although we swam mostly in wet suits in one of the more public pools on the first afternnoon, later on after setting up camp I introduced them to traditional skinny dipping.
These days, my walking in the fells is almost entirely barefoot and I always look for somewhere to skinny dip. If I can walk 'skyclad' as well, so much the better, although there are fewer chances to combine that with swimming as the quieter spots have fewer tarns and suitable mountain becks. Of course, just wearing a pair of shorts and maybe a t-shirt, it only takes a moment to be in the water and usually I can dry off in the air.
I have also been spending increasing time in the local woods, which are great fror walking in barefoot although I go off path a lot and have rediscovered tree climbing, barefoot and skyclad, of course. See tree hugging thread. The problem going off path is that sometimed I come across patches of brambles etc which are difficult to get around barefoot!