I shot a sequence of photos of a waterfall in Wyoming last week to demonstrate the changes in appearance of the flowing water at various shutter speeds.
1/250th - 1/125th - 1/60th - 1/30th - 1/15th - 1/8th and 1/4 second respectfully
With my camera firmly mounted on a tripod I varied the aperture value to give me single step shutter speed changes from 1/250th second to 1/4 of a second. The changes in appearance are quite easy to see and should help you pick a combination you want to use for moving water and waterfalls.
1/250th of a secondBrooklyn Waterfall in the Absaroka Range of Wyoming. Canon 5DIII and Canon 70-200/2.8L IS lens on a Feisol Tripod and Feisol Ballhead
1/125th of a second
1/60th of a second