How to freeze a waterfall
Aside from in Harry Potter books, photographs don’t move. This gives you choices in what to do with motion. A subject’s motion can either be frozen with a fast shutter speed or implied through blurring with a slow shutter speed. Using a fast (1/1600 sec) shutter speed, the water looks sharp like ice or glass.
You might prefer your waterfall more romantic and blurred, however, like a gauzy bed canopy. Use a long shutter speed (this one’s at 1/4 sec) and voila!