WTF? How is there weight in water? It contains no calories.
My advice for anyone taking a sport seriously at any level is to drink water to the point of it being physically inconvenient. As long as u maintain electrolyte levels thru a good diet (most ppl do without trying) it will have huge benefits to ur training once u get it right.
I drink 6-7 litres daily to help keep me stronnng.
The September issue of Muscle and Fitness says it would take 15 3/4 cans of tuna to lose weight, and they're usually right about most bodybuilding subjects.
Hope this helps.