Eight... seemed at least plausible. Eighteen was too much of a stretch for the half-elf to believe it, giving the joke away. There is a slight, slight pause from the shapeshifter when Tidus mentions his extra limbs, but he's quick to reply, half apologetic, and half amused by the argument.

"Yeah, but fire lungs' 's the one thing I didn't inherit; I used t' eat super spicy foods as a hookling tryin' to get them t' grow." He'd been really disappointed when they just didn't. But, well, people are ingenious, and he found out that anyone could do it, really, with a bit of practice.

"I might've gotten jealous 'f you really had extra lungs," he chuckles, at least free to admit that much. But, practice, hun. People truly are incredibly ingenious. "How long c'n you stay underwater? Without gettin' a new breath?"