"Why do we get thirsty-is there anything we can do?"

We get thirsty because our cells cry out for H2O. You could tie your pecker in a knot, plug up yer arse with a cork and THEN drink sufficient (but only sufficient) water to assuage that thirst. You will then become a self-contained eco system for a short time before you turn into a toxic waste site. It's not the same answer you'da got from Ann Landers, but then I ain't Ann Landers.