It's interesting. Not sure i like all the negative space with the B&W treatment. Border catches my eye in a bad way. I do like the creaminess of the water motion.
Whilst I appreciate the high-contrast and high-key elements of the image (an idea to hold onto for the next high-key challenge, actually), I find the progression to the white negative space to be pretty sudden - perhaps a function of your low point of view as much as anything, but nevertheless a bit abrupt. That very abruptness works against the image sitting well in the square crop also, I think: interesting work, but perhaps just short of outstanding for me.
this picture would be mazing with a intense clouds, because you had to slow the shutter speed to blur the water, you lost all detail in the sky, and thus lost this competition, using a grad grey filter or grad polorizer filter could have saved this image, go back some time right after a storm/or right before and look for intensity in the sky, capture both the flowing serenity of the water and the dark intensity of the sky and you have a winning photograph