Were it anyone else sassing him about his lack of a sense of humor, he would've sassed right on back. But this is Toph, and he gets it. There's too much water, no land in sight. She's an earthbender who is literally out of her element with only the metal on this ship for her to peer through and see in that way she's learned to without the use of working eyes. She's mad, and she has a right to be. He doesn't blame her, and he'd rather have her snapping at him than biting someone else's head off.

...or looking at him like that. He knows that look.

"You're about to remind me about burning your feet, aren't you?"

He's about to become a living palanquin, isn't he?