Thinking of his puny human body, Derrick wrinkles his nose. "I don't really want to go back to the old me, but this is just the first few hors of a two-week vacation. I don't want to spend it all as a horse or centaur." Hephaustus chuckles. "How about returning to yourself with enhancements? You can experiment all you want and providing you don't end up as something else, it will be your form when you return home."
"What have you got in...?" Derrick's question was cut off as he suddenly felt dizzy and the world around him got larger. When he felt OK again, he was human - but not quite what he'd been before. The equipment between his legs was definitely equine is size and shape, and even more potent if the dribble of semen from the tip was an indication. And he still had a horse's tail. But the human parts looked different as well. Human, but well muscled and smooth, a 15-year-old swimmer or gymnast. He moved to the pool and looked at his reflection. Easily recognizable as his old self, but with horse's ears and a mane that ran all the way to his shoulder blades.
"Oh, wow!" Derrick grinned. "I can keep all of this?" The centaur nodded. "That is now you, only changeable if you allow it." What Hephaustus did not say was that the 'godling' essence that Derrick had enjoyed was still there, so that whatever he chose to be, he would stay that way. So in a hundred years, a thousand, he would still be the 15-year-old horse-boy he was now. Or maybe a full horse, or a minotaur, or an infant. Whatever he left the resort as was his permanent shape.
"Thanks!" Derrick ran back towards the Spa, planning on meeting the rest of his family when they got back to the tour. Hephaustus grinned as he watched the still-naked youth jog away, knowing Derrick no longer thought of clothing. Derrick got back to the Spa and went to reception. The girl there nodded in approval. "Very nice! Your family isn't back yet. Poseidon is just over there. I bet he would be happy to see you. He is the God of horses."