Back in the days when I had the time, I used to do lots of climbing and mountaineering and it was always good to cool off in a mountain tarn or a stream at the end of a long walk or bike ride. One of the best ever was the Etive river, which runs over flat glaciated slabs on Rannoch Moor and is solar heated by the time it drops down the glen. My cousin and I found a glorious rock pool a good 50 yards long and deep enough for diving, warm, clear and with several freezing waterfalls pouring in off the mountainside above. My wife and I spent our first night together camping on a small peninsula in Angle Tarn above Patterale and skinny-dipped in the morning. We also often swam in burns when we had come down off the mountain during our honeymoon, which we spent climbing in Scotland. There's nothing better than wild swimming, as long as the water is warm enough.