Steven's been, up till this point, using vines and his shields as best as he can to hold off the wylderkin. Once the water starts rising, though, he has to readjust his priorities. Most of his friends can fly or already have help... but then there's Jasper.

He can sense her fear immediately - more than what would be there from the threat of water alone. He only hesitates for a moment before leaping towards her and spreading his wings.

"Hang on," he gasps, getting beneath Jasper's horse body and grabbing hold with his arms. "We're going up!"

He pushes off the ground with all the force he can muster, launching the three of them into the air as he struggles beneath her probably kicking horse legs. His floating powers and strength enable him to lift her, but there's not so much room for carefully planning the trajectory. Also, he's never deadlifted a horse before.