Okay. So she's an alien. He can wrap his head around that one, without needing to get too deep in the human ancestry thing.

"I can't say that I've ever met anyone not from the planet Earth before." At least, not explicitly not from Earth. He hasn't exactly been questioning the few people he's run into.

"So your kind is adapted to more easily live in the water, then? That would be useful, in a place where the water is accessible and clean."