I spent last week hanging out in the Hocking Hills State Park in southern Ohio, hiking some of the trails and looking at waterfalls and caves. Here's a photo of the upper falls near Old Man's Cave (click on the image for a larger view):

It's a little misleading in that the place was teeming with tourists when I took this photo. I did not have a tripod so I took a bunch of images at the lowest shutter speed that I could reasonably hand hold the camera - 1/8th of a second. It was a decent compromise in that any single image what reasonably sharp and the water was slightly blurred. Post processing the images today, I stack focused the group in Photoshop and that increased sharpness considerably by blending the sharpest bits of each of the 29 exposures. I then averaged the exposures and that created a more pronounced blur in the moving water. I blended just the blurred water from the averaged composite into the focused stacked composite for the final image. It would have been better to use a tripod and a ND filter, but this way I didn't have to carry so much while hiking.