The second photo was taken at a shutter speed of 1/500th of a second. If you look closely, you will see the water drops frozen in flight from the waterfall, and can see the different way the moving water is reproduced compared to the first photo.
Check your camera's owners manual to see if your camera allows you to manually adjust the shutter and aperture settings. Remember that when you change one of the settings (shutter or aperture) to get the affect you want, you also have to set the other one accordingly. Some cameras, particularly digital SLR's, have the choice of aperture-prefered or shutter-prefered settings (marked A or S) that let you make your choice and then automatically set the other exposure setting for you. Also, use a camera support like a tripod for best results when using long exposures (like 1/15th or 1/2 second) unless you are experienced at handling your camera in a steady manner.