In order get that creamy waterfall during daylight you need to have a neutral density filter. This cuts down the light coming into the camera so that you can have a long exposure even in broad daylight. Nowadays there are multi-stop ND filters like this where you can rotate the filter to change the intensity which is the most versatile option. Thanks to digital you can play with exposures and see how long you need to get that blurred effect but at least 1/2 a second. Also you want to make sure you avoid camera shake so weight down your tripod and either set the camera on self timer so you don’t accidentally shake the camera when you press the shutter or use one of these nifty and cheap camera remotes.

Canon 5D Mark III, Canon 24-70mm f/2.8 lens. ISO 100, F/20, .5 seconds. With neutral density filter.