Mark remembered the transformation out of the water had been painful for Amy and she had said it was painful for Lina too. So he removed his boxers and slid into the pool before putting the necklace on. The changes were almost immediate but almost painless. Mark's legs merged into a tail and his feet flaired into fins. He experienced the strange sensation of his penis retracting into his tail. But the changes didn't stop there: he felt his hair lengthen down to his shoulders and his chest expand. The strange sensation in his groin continued as his retracted penis became a vagina.
He wasn't completely surprised by the last part of this change. The way Amy had stopped him from putting on the necklace originally. "Turns you into a mermaid." "Become like us." Hell, what guy would wear a pearl necklace? He'd fantasized about being with a mermaid, but not becoming one. But if it took becoming a mermaid to have a threesome with Amy and Lina he was okay with that.
Amy and Lina swam up to him.
"So how do you like being a mermaid?" asked Amy.
Mark responded by wrapping his green tail around Amy's orange tail and Lina's lilac tail and pulling the three mermaids together. All three of them were smiling.