Bedtime, after lights out.
Felix: Daddy, I have a question--wait, I have two questions. Why is there salt water in the oceans and why if we drink it are we always thirsty? Those are my two questions.
Keir: Wow, those are good questions. I'm not sure why there is salt water in the oceans...maybe the oceans have a lot of minerals in them? Salt is a mineral, and maybe the ocean floor is very salty. I don't really know. But when we drink salt water--remember how cells, and every part of our body has water inside? If we have too much salt in our bodies, the salt sucks the water out of our cells and then our bodies tell us we're thirsty so we drink more water, but if it's salt water it doesn't do any good. You could have a tummy full of salt water, and you could have to pee a lot, but you would still be thirsty because your body wouldn't get what it needs. (Thinking, Whew.)
Felix: That doesn't sound like a very good way to live.