Photographing waterfalls with misty blurry water is an all time landscape classic which depends on using a very slow shutter speed. They look fantastic and always impress the viewer.
But you have to be very careful to get the exposure right or the white water will burn out and the picture will be over bright.
Photographing waterfalls takes a bit of planning. For example the weather plays a big part and you might need to use ND filters too.
Professional landscape photographer Tom Mackie and I went to the lake district a couple of years ago and shot a series of Landscape Photography workshop films for Digital SLR User Magazine who have kindly given us permission to produce a 'directors cut' version of the films we shot.