He sets his backpack in one of the seats. "Now, I don't have enough water with me to turn all the way back, but I can show you some of it."

Pulling a bottle of water out of his backpack, Luca opens it and begins pouring it on his arm. As water touches skin, green scales quickly take it's place, and a blue fin emerges from his forearm.

"It's enough to give you the idea, anyway."

After a little bit, as his skin begins to dry, his arm changes back.