For a moment, John loses his focus - or whatever small focus there is on this stupid little thing they're doing - because he can't for the life of him figure out where that came from. Captain Watson and boat terms all of a sudden. He's surprised, and there's more laughter because of it, but he shrugs and goes with it. Grabs a book, throws it up and sends it to the far left corner.

"If I'm captain, what are you, then? Or are we both captains?"

He doubts that ever happens on one ship, but who cares? Their ship, their rules, or something like that.

And suddenly this room is a ship, apparently. Why not?