David floundered in the water, even more than he had while practicing that difficult stroke! His legs bucked from the wild sensation that surged within them. His body, and mind, too, were being played with by some tingling, electrifying force.
As the pressure built, David bucked his legs as hard as he could. Some primal thought in his head told him there was something terrible to them. Something about him had to change!
He pressed his legs together tight, threw back his drenched brown hair, and bucked once again. His legs had started to broaden... to widen! His hips filled, becoming bulky and fat, while his bound legs did the same, though in a very streamlined way. His swim-shorts snapped away, leaving him entirely naked under the surf. Those broadened, bound legs of his lengthened, stretching to a length quite possibly twice as long! His toes wriggled, before they struck together too.
From the crotch down, his legs began slowly merging. The further his legs merged, the more flexible and unstiffened the bone within them became. The luxurious feeling of it all hardened his member, but in his ecstasy, he couldn’t have cared less who saw!
Soon, his legs had fused into one, massive, broad limb. It tickled as hundreds of shimmering aqua-blue scales enshrouded the limb as they grew upon it.
His feet flattened, and lengthened into two large, fantastic tailfins of a brighter blue. There was no remaining evidence that he’d ever been legged.
His penis was absorbed into a sheath in his tail.
Happily exhausted from the orgasmic change, he gave his tail a mighty swish! Wonderful! It could bend and move any way he wished!
He was a Merman! A Merboy!
In a moment of joy, he pumped his massive tail, and broke the water’s surface as he jumped!
Ms. Maisar gasped as she saw. Well, very few of her potions had had that fine an effect! He must have really wished for such a thing... She smiled proudly. She picked the right guinea pig.
David soared off into the sea. Never wondering for a moment how it’d happened. Of all the wondrous things now open to him, what would he choose?