I'm not an expert on the subject, but as far as I know, oil, even cooking oil would do a better job than water because of the boiling point.
When you dunk hot metal into water, the water "flash" boils which creates pockets of steam between the water and your blade, bubbles running around on it and such which could very much give you an uneven quench. That's not to say that water dosn't work, the Japaneses have been using water for the worlds most revierd blades we know.
So if you're gonna use water, use a relatively large quenching tub so you can keep your blade in motion while inside the water so you get constant contact between your blade and the water.
http://www.youtube.com/watch?v=oijgODuKzeo&playnext_from=TL&videos=F1HqH1-K_IY
This guy is quite informative in his vid's, maybe he'll be of some help.
Enjoy,
Ami.