I'm guessing the water came crashing every once in a while, and he shot a 0.4sec exposure when he heard/saw it coming (on a tripod, of course, possibly remote triggered).
And he exported it in Aperture 3.4.2.
I would say this scene is quite plausible, though out of the ordinary. What bothers me most in verifying the validity of this is the still-water rather than the moving water (which, again, is entirely possible).
An exposure time of 0.4s would blur the water traveling at this velocity, and create the lines we see (similar to this http://i.imgur.com/MyZmwMd.jpg ). But, yes, it's still possible it was Photoshopped.