As jrw pointed out, when you slow your shutter-speed to blur the water, you will increase the amount of light hitting the sensor and therefore your image will be overexposed. You can buy a Neutral Density (ND) Filter, which is a dark filter, like a pair of sunglasses, which will hold back anywhere from 1-stop to 10-stops of light (or adjustable ones), thereby allowing slower shutter-speeds without over-exposing your shot.

ND filters come in various sizes which can screw on to the front of your lens:

http://www.adorama.com/catalog.tpl?o...ature1=B %2b W

To view images on the LCD in bright sunlight, I use a Hoodman Loupe:

http://www.hoodmanusa.com/products.asp?dept=1017

For video you can buy the attachment kit package or less expensive Cinema Strap, so that you don't have to hold it in place:

http://www.hoodmanusa.com/products.asp?dept=1066

Rich