Outdoor swimming (now more funkily called wild swimming) in a natural pond, filled only by rainwater is an amazing chemical free experience.
We have installed pumps to keep the water moving, planted filtration plants that clean and aerate the water and cleared the canopy so it is open to the sun. It is naturally clay lined and is 11 feet deep so gains a lot of warmth from the ground.
We use it several times a day in the summer and now with our outdoor sauna we use it in the winter too.
Come try it out as part of a personal training package or a retreat package - it's heaven!