The other day at Snoqualmie Falls in WA, working on soft, dreamy water in daylight using ND filters and tips picked up from PTW1. I took advice to use a slower shutter and am really happy with how the water looks, but feedback and constructive criticism are always appreciated!
Canon 80D and 24mm f/2.8
ISO 100
f/8
2 sec exposure w/ layered 6-stop and 3-stop ND filters
Look and feel of water is so subjective, however, I like what you've done with the scene. The mist and soft water work well with the rainbow for me.
Only adjustment I would have made, is compositional. If I frame to including the top of the falls, I like to give a little more breathing room. Otherwise, I might compose with half of the falls to highlight something cool in the foreground.