All these are great answers, but I wanted to remind everyone that water is integral to almost all the functions of the body. Without the proper amount, you are putting constant stress on the body. I think we need to emphasize drinking proper amounts of water, whether it helps with weight loss or not.
Also, if you are taking supplements, many have caffeine and/or protein. Caffeine can be dehydrating and extra protein puts stress of the kidneys. If you are taking supplements, you need to be even more conscious of the amount of water you drink.