Enough Water?

This post isn't about conversion of water, because frankly if that was an issue it would be on the news more often; instead it's the minuscule ad in the corner of a website.  When I say "enough water,"I mean enough water for our body, do we really drink the suggested 6-8 glasses?  I never was able to figure out how big a glass actually was, so when I was little I would drink 6 of the smallest glasses I could find and drink that: I hated water.  I was inspired today by my biology teacher who was talking about needs of animals and how people needs 6-8 glasses of water.  The whole class might have just laughed because I am pretty sure none of us drink that much water unless we are athletes or they are weirdos who never want to stop going to the restroom.  I wonder what the exact measurement of water is truly enough water.  Do you ever think of that?