You pull your dick out of her pussy, kissing her again. "That was amazing," she whispers, giggling slightly. You lie down, letting the sun warm your body. Eventually sit up and slide of the rock, into the water.
You swim around, brushing against some of the merfolk's tails. The water is cold against your balls and cock. Your curly brown hair floats in the water around you.
You swim up to the surface, pulling yourself onto the rock. Your hair falls on your shoulders. Your pubic hair is flat, climbing up the base of your cock. You turn to Joan, who has been watching you.
"I want to be a merman," you tell her.
"Alright," Joan says, smiling slightly. "Follow me."
She pushes herself off the rock, and swims along the edge of cove. You walk just behind her. She leads you into a cave.
At the end of the cave is a fountain, shaped like a humanoid face, with it's mouth open, spilling crystal-clear water into the pool. A hole in the roof above the pool adds to the mystical effect.
"Just bathe yourself in that water," she starts. "And you'll become whatever type of merperson you want."
You jump into the pool. It's is freezing, especially against your balls. You feel the magic begin to wash over you.