"Why, a ship ye sail on the ocean, of course!" He looks at Kaylee with an utterly baffled expression on his face as she talks about 'spaceships' and 'planets'.

After a moment, he frowns and asks, "Are ye feeling ill? I could go see if there's some leeches if ye are." Maybe she's running a fever and that's why she's talking nonsense. Being bled should help with that.