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.
If you have a swimming pool you should make the best of it! Get awesome compliments when you invite your friends for a bbq near the pool! Don't settle for the same old style, get inspired by our 30 swimming pool ideas that will upgrade your outside space.