He's following, nodding along, having some basic of comparison even if competitive sports weren't a big thing in his world-- and then Tidus just had to go and drop something like that on him.

"Under--" Surprise catches his breath from his lungs, and the sheer look manages to convey more shock than Esteban can truly say, this sort of baffled what-the-hell glance that widens his eyes. He has to make sure he understood that correctly.

"All of it? Underwater?" He pauses for the confirmation, blue eyes searching for a trace of a joke in Tidus' smile, or the tilt of his head. But it seems... honest?

Processing. Wrapping his head around this. And of course, the first questions that pops out.

"Do you have gills?" No wait-- "How many lungs d' you have?!?"

A perfectly legitimate question. C'mon Tidus, cut him some slack, this is Clearly Not Normal for him.