You turn away from the mermaid as she reaches out for you. Slowly, she suffocates, her body falling limp. You turn back to her and her body turns to ash and disintegrates. You are all alone now. You lay back against the side of the pool, letting water from the fountain fall over your head. You then dip down under the water and fall down to the bottom of the pool, you spot a tunnel inside the pool, possibly the way out. You then look away, not caring about a way out, something happens inside your body as you jet back up to the surface.
You reach the surface and lay your hand on the rocks. Your hand begins to change, growing grayish as claws push their way through your fingernails. You then look down at your breasts as they grow twice as big and are covered over by a layer of gray leathery flesh. Then, your body is racked with pain. You scream in agony as the fountains stop. Your other hand changes, both of them now covered in webbing. You grab your head in pain, tearing out all your hair in large chunks.
Then, your dorsal fin extends and grows shark-like as your fin changes as well, becoming more fish-like, more like a shark. Then, you spit up blood and several teeth into the water, in their place, sharp shark teeth extend from your gums as your eyes turn jet black and the final transformation begins, you shed what's left of your mermaid exterior and look at your reflection, with almost no emotion, you ignore your appearance and jet under the water.
You swim out through the tunnel, possibly to be stuck as this forever.