Peridot doesn't really get how the human body heals. She's never really seen any of them injured and Steven isn't exactly the best baseline, since he's part gem. So when Ellana seems mildly amused at the idea of just fixing it, it makes Peridot a little frustrated. Why are humans dumb? Sure, they don't work like gems, but they have to be able to fix themselves when they break. Don't they?

"You know... get another one? Or whatever it is humans do when they get hurt?" She sounds like she's explaining the concept to a small child. Which is a bit strange, because she's not exactly looking down at Ellana (well, not in the physical sense). She shakes her head.

"Why would I want to go swimming, anyway? Or go up? It's wasted effort. We've got a job to do down here, remember?"