Pharell Williams
Pharell Williams has actually had to go so far as to go on the record saying that home does not drink human blood, because it is so unbelievable to people that he has been able to keep from aging. He credits constant exfoliation and drinking plenty of water for being able to slow the aging process down to a crawl.
The fact that he has looked the same for the last two decades should prove that his methods, whatever they may be are working. Now I know he says that there is nothing magical to it, but I still have my doubts. If there is no change after another twenty years, you might want to think up a better reason than just staying hydrated.