50-70%. At the age of 1, percentage is around 65%. In adult men, 60% of their bodies is water. 55% of adult women's weight is water due to fat not holding as much water as lean tissue; fat makes up more of women's bodies than men.
I am thinking it is by heating themselves in sunlight. I think this because when I bring lizards to mind, they are cold blooded, and they need sunlight to bath in so they do not start to lack warmth to live.
I hope this helps.