You need a much slower shutter speed. You can get some blurring with a half-second exposure, and the full cottony effect with an exposure of several seconds. So the short answer is, set the camera on manual, set the shutter speed to 2 seconds, set the ISO as low as it will go (80, I believe), and the aperture as small as it will go (i.e. set the F stop as high as it will go, which is 8.0 on your camera, I believe).
Unfortunately, you may have had too much light in that scene for the slow shutter speed to work. According to your file, you used a shutter speed of 1/80th of a second at F4.0, using ISO 100. With an exposure of 2 seconds, F8 and ISO 80, you would have let in 32 times as much light, which would give you a badly overexposed photo -- and your water is already overexposed.
So to get the effect you want, you can either buy a strong neutral density filter to cut down on the amount of light getting to your lense, or (much cheaper) take the picture at dusk.
Of course, for a 2 second exposure you'll need that pesky tripod again, or some other kind of support system -- a 2 pound bag of beans or rice works well, as long as there is a handy surface to plop it on.
