Blackwater Falls, Blackwater Falls State Park, WV

The images above show how shutter speed could be used to improve your nature photos.  These two images were taken at Blackwater Falls State Park, WV.  The image on the right was taken at a shutter speed of 1/800 second.  Note the choppiness of the water as it flows over the falls and how you can see individual drops of water in the splashes.

The image on the left was taken using a shutter speed of 1/6 second.  Note how the water almost appears to be a veil covering the rocks.  The left image appears to be more peaceful and less anguished than the right image.  While the right image presents the falls as our eye sees them, the slower shutter speed on the left makes for a more pleasing image.

Of course, there are times when one would prefer the anguished look of the right image, but in general, waterfalls should be shot at shutter speeds less than 1/60.  The slower the shutter speed, the more of a veil effect you can achieve.  However, a longer shutter speed used on larger falls could result in a white blob on a rocky background.  The shutter speed you decide to use will depend on the desired effect and how you want to compose the scene.