Waterfalls dont create ozone, they just disperse it. In nature oxygen is released from plants and sea plankton during photosynthesis. Oxygen floats upward into the atmosphere and in turn is converted into activated oxygen by ultraviolet radiation. A waterfall moves large amounts of water, and displaces large amounts of molecules. This is why you get a good, clean, or almost euphoric feeling at the beach or near a waterfall.

Someone correct me if I'm wrong.