The movement of water can help to create interesting images. In order to capture images such as these it is essential to use a tripod, as shutter speeds close to 1 second or greater will be required. Generally a shutter speed of 1/8 of a second will start to blur the moving water, but with a tripod any shutter speeds up to 1/2 minute can be tried. Sometimes it is useful if a neutral density filter is used so that longer shutter speeds can be used.
Waterfalls are great to capture the movement of water, also fast flowing streams aroud rocks also can form interesting images.
As well as a tripod some sort of cable release shgould also be used to avoid any blur of the image due to movement of the camera when operating the shutter.
There are further details on tripods and remote camera controls on articles as follows.
Gorgeous creamy effect and lovely blue tones. Great advice too. It takes a great eye too though to produce compelling photos like these.