Deciding upon a favorite animal of his, John returns to the edge of the pool, sliding his way along, trying to keep from damaging himself in any way.
He reaches the edge, Mary looking expectantly at him, trying to get a sneak peek of what he's cradling in his hand.
"No peaking! You didn't let me in on it, so now I'm doing the same," John teased her.
"Fine, fine, but this better be good!"
Realizing that he would have to use the human vial to return to normal first, he took a swig of the entire bottle. Capping it, it returned to it's full state.
The effects were almost immediate, his penis slid back out, returning to a more manageable state, while the rest of his body bulked up, the muscles defining themselves in ways he'd never had before.
John decided that Mary's larger vagina would be better for what he had in mind, John told her to turn around, while he slowly slipped into the pool. He gulped down half the vial, getting ready for something he had only fantasized about before.
His legs slowly split, multiplying until he had eight slim, slightly red appendages, with multitudes of suckers growing on them, lengthening, and slowly thickening.
When done, John's lower body had turned into that of a large octopus, with his torso remaining muscular and human.