I don't think you are gaining water by taking anavar. At least not much water. I think you're just getting great results because you're well below your genetic potential and using steroids for the first time, at a healthy dose. Enjoy it while you can. Personally, if you can't get more, I'd consider dropping the dose to 30 mgs. per day and stretching it out longer. My first AS was anavar and I never used more than 20 mgs. per day (granted it was Searle), and gained about 15 lbs. over the course of 6 weeks or so.