"We breathe air," Jake said, pausing as he rejoined with Banshee, "because we have lungs and we're not part-fish. The air back home's different again. The gravity's weaker and the air is denser. Tawtutes can't breathe it at all, it kills them."
He climbed onto Banshee, and then looked down at Cris. "Hold on, as tight as you can. Yell if you need my attention. And which direction do you want me to go?"
Banshee clearly didn't feel the need for such checks, and let Jake know he was taking off about half a second before he actually did.