Someone asked on Flickr how you get waterblur in your photographs.
You can go into aperture priority stick and stop down to f/22 to get waterblur, but you are hitting the diffraction limits of the lens and losing sharpness. (Remember, if you have a polarizer hanging around, it doubles as an 2-stop ND filter. If you have a pocket digital camera, your sunglasses can be a filter in a pinch.)
ND filters and a tripod are your best bet. A neutral-density (ND) filter allows you to experiment with waterblur on a sunny day:
You actually don’t need an amazing slow shutter speed to get a decent blur. The rule of thumb here a photo at 1/30 or 1/60 will be the same blur as your eye. So anything an order of magnitude faster will “stop” the shot and an order of magnitude slower (say on the order of a second) will blur it.
You might want to purchase a variety of ND filter densities. Instead of this, I use a Singh-Ray Vari-ND filter—it’s not cheap. Since it is two stacked linear polarizers and a half wave plate, it’s not small and I get some vignetting on my 12-24mm @ 12mm. Also, if you dial it up too much, the whole photo gets some weird red shifting in a “+” pattern down the center.
One parting tip: Don’t trust your metering system. Why? Because the metering system samples too fast and doesn’t see the waterblur. This means inevitably it will tend to overexpose and you will be left with some seriously blown out highlights where the water flows. Either underexpose by a 1/2 stop or, better yet, take multiple exposures and use contrast blending or HDR to recover the blown highlights from the shot.