It seems that water is the perfect medium to give it that slow graceful movement of the massive ship it's supposed to be.
With a little imagination, the lighting and background of the pool they used to film reminds me of the star base interior from Star Trek III.
He apparently has created a few of these. there are a few more videos from the creator of Voyager and the Millennium Falcon.
And NO, It doesn't look like they're for sale.
http://www.youtube.com/watch?v=zQEsG4eKIXs
