Hey!
As far as I know, only increasing the amount of water you drink will have no effect on fat loss, which is what you want to lose. It may reduce some water weight because it flushes out salt, but that's not the point of a weight loss program.
It's a good idea to drink plenty of fluids (and water is usually what's meant)while on a weight reduction program to make sure your body is flushing out the byproducts of fat metabolism. These byproducts can be dangerous if they are excessive.
So, wish I could tell you that just drinking water would help! But IMO, it won't do much by itself.
Jay