In Europe, natural swimming pools are an increasingly popular alternative to chemically maintained pools. Plants act as a natural filter and harbor beneficial bacteria to keep the pool clean. No chlorine or salt needed. in garden homesteading ^^
Natural Pool- your pool looks like a natural pond Chemical-free water garden and swimming pool. The plant portion, or regeneration zone, is separated from the swimming area by the wall seen a few inches below the water’s surface
Natural landscape architect and garden designer Michael Littlewood of Somerset, UK. Designer of natural swimming pools. Author of Natural Swimming Pools, Inspiration for Harmony with Nature, available on his website.
An alternative to chlorine pools, the BioTop Natural Pools use plants to keep water clean and clear. Wikipedia has some more info on natural swimming pools as well. These could make a great addition to a permaculture design site.