As a mechanical engineer I would be interested to see how much heat a certain sized water tank could absorb. My gut is with the previous posts that it would not be enough to be an effective heat sink. However, it is a fairly simple problem to work out if you have all the numbers. I'm a bit too lazy to actually figure it out for you. But, if you have any like minded nerds you know it might be fun to get out the old heat transfer text book and calculator to figure it out over some beers.