Mary can't resist trying a new vial. She looked over the choices, but they all seemed so ordinary. Then she spotted a drawer below the Bird and Age drawers that seemed interesting. A little label said "Mythical." She opened it, revealing even more vials. The pictures on these vials were obviously fairy tale creatures, from centaurs to harpies to different kinds of dragons.
One picture had a female body, but the lower half ended in a fish tail. "A mermaid!" Mary cried gleefully. "Perfect!"
She uncorked the vial and brought it to her lips, but paused for a moment. Thinking about what she was about to do, she took the vial with her into the bathroom.
In no time, Mary had the bathtub full of warm water. She then poured the entire vial into it, stirring the water gently with her hand. She removed all her clothing, neatly piling it on the floor, and stepped in.
The warm water felt very relaxing as Mary dipped her entire body under the surface. She even dunked her head down for a few seconds, making sure her entire body was completely soaked. Then she laid in the tub with only her head above water, resting against the tile wall.
The minutes passed, and Mary watched the bathroom mirror slowly fog with steam as she lost herself in the warmth of the bathwater. The heat expanded all her pores, allowing in much of the magic-infused liquid.
It took a little while, but she eventually noticed subtle changes. First her skin began to turn very smooth. It looked and felt even better than it had with the extra changes made by the Female vial. Then she felt her hair growing even longer. She ducked underwater one more time, just to make sure it was getting enough of the potion.
Her legs began to join together, starting at her midsection. Her vagina moved forward to right below her stomach, no longer having a crevice to inhabit. The merging spread down to her knees, which flattened into nothing. As this continued, blue-green scales grew across her legs. They were pebbly to the touch and had a dazzling shine.
Once her ankles had been overtaken by her emerging fish half, Mary no longer had any firm joints below her waist. She lifted her feet--which barely fit the description anymore--out of the water to watch as her toes spread out, silky webbing forming between them. The pinky toes grew the longest, about two feet, as they split into dozens of thin, flexible support ribs. Her two half-fins joined to create a unified fin that was wider than the bathtub. It had the same blue-green hue as her scales, and the webbing was so thin she could partially see through it.
Mary now had a fully-developed mermaid tail. It ended at her waist, making an upside-down V border as it merged with her skin just below her belly button.
However Mary found that her changes weren't finished yet. The human skin on her sides between her ribs and waist split open. Three horizontal slits formed, about five inches wide, and the skin above them grew to overlap them, almost like window blinds. Mary stared curiously as the newly-formed flaps opened and closed. She gasped in delight, giggling at the prospect of gills. Could she really breathe underwater?
She had no sooner thought this than felt a pain in her back. She sat up a bit, feeling behind her. Apparently the skin there had grown scales as well, though this growth into her human upper half seemed confined to her back, not her sides or chest. Out of her spinal column she could feel more thin ribs like those on her tail jutting out of the scales. They pushed out, growing webbing between them, to form a semi-transparent dorsal fin. It began at her shoulder blades and fanned out from there, its connection to her back ending between her gills. Mary guessed, from what she could see, that the fin extended out nearly a foot behind her.
More small fins made themselves known on her forearms. There, tiny spines grew from a thin patch of scales, forming fins that ran up to her elbows and flared out to a point in the air. Her dainty hands grew thin webbing halfway down her fingers. This time, however, the skin was its regular color. Her fingernails, however, did turn blue-green, accenting the change. Her hands remained otherwise as delicate and human as before.
Then she felt something tugging on her ears. Bringing her new webbed hands up to investigate, she found that they had flared out like her fins. Both ears grew three ribs that made vertical fins six inches long from her earlobes. To top these off, another fin emerged from the top of her head. It joined with smaller ribs as it traveled down to the back of her neck, tapering off and finally disappearing into her skin before reaching her dorsal fin.
Mary was absolutely delighted by the changes. For a few minutes she idly flapped her giant tail in and out of the water, now feeling very cramped in the bathtub. "Obviously it wasn't designed for mermaids," she joked to herself. She reached for a small mirror atop the toilet and looked into it. She saw the fin atop her head, as well as the fans emerging from her ears. She was surprised to see that she had developed a strange glitter around her eyes. Her skin remained the same color it always had, but now it possessed unnatural sparkle. To top it all off, her hair had changed color. It was now a brilliant emerald green, wavy and vibrant. Somehow it still looked stunning, even though it hung off her head as damp as it was. She followed a lock of it with her scaly hand to find that it had grown much longer. It went as far as where her knees had disappeared, halfway down her mermaid tail. Most of it, though, was gathered up and floating around her shoulders.
Mary continued to explore her body, feeling the changes and reveling in the almost unbelievable fact that she had been turned into a mermaid. She even tried ducking completely underwater and letting her gills do their work, while she felt the rush of water going in and out of the slits. "If only I wasn't confined to this small tub," she wished silently.