I think that makes sense, water is absorbed into the bloodstream, right? And then the kidneys filter the blood and the bad bits + excess water is peed out. Which is why your pee looks saturated yellow if you are dehydrated and almost clear (but don’t drink it!) when you have drank a lot of water.

Any remaining water in your digestive tract that isn’t absorbed would be in your poos! If you have diarrhoea and your poos are all liquidy, that means water is not being absorbed properly (bad!)

I didn’t do Biology, I’m a Physics+Chem student, so this could be completely wrong!