Wow, really nice. I really good see a message being expressed int that. First it expresses the lgiht, calm playful nature of water and then the crushing power of the waterfall. Next, I kind of saw the area underneath the water waterfall, with less light, lots of bubbles. Then is kind of saw the process starting all over again.
I don't think I can give any good advice on techniques and stuff, but I really liked how you had somehting gliding quickly in the background a lot of the time.