Huh, he wonders why it worked on her...although maybe that's just not how it actually works. He doesn't know. It doesn't matter. Once Luz grabs on, he takes off through the water, using his powerful tail to bring them back to the boat. He looks around for a bit until he finds some rope hanging over the side. He swims close to it so she can grab on.

"Hurry up and get back on the ship!"

And he definitely wants her to go before he does, because he has the feeling Luz is in far more danger than he is.