What distinguishes a natural swimming pool from a traditional one? The main difference lies in natural pools' independence from artificial filtration. That doesn't mean jumping into a natural pool leaves you with a mouth full of algae. On the contrary, plants and other biological agents maintain the water quality, leaving the swimmer to enjoy a chlorine-free experience. Rather than obstruct the swimming area, the plants are focused in what's known as the regeneration zone, either directly adjacent to—or completely separate from—the swim basin.