Back in the bathroom, Mary placed the vial box on the sink. She folded a hand towel and placed it on the tub's built-in soapdish. Then, she filled it almost to the brim with water. This time she made sure the water was cooler, as her scales seemed a little annoyed at her previous warm bath. Then, as she sat next to the tub, she swallowed everything in the Mermaid vial. She corked it and set it on the towel, then pulled out a vial labeled "Shrink." Unsure of exactly how much to take, she gulped down all but a quarter of it before corking that and setting it on the towel as well. Finally, she pulled the Human and Growth vials from the box and placed them next to the other two, well within reach for even the shortest of mermaids.
She felt the familiar sensation of scales rippling across her body as her legs were once again pulled together to form a tail. Her hair turned a deep, dazzling green and grew out. Fins erupted from her arms, back and head as webbing grew between her fingers. The changes happened faster than before, and Mary guessed it was because she drank the vial instead of soaking in the formula.
While she had transformed, however, she had failed to notice the tub slowly getting larger beside her. When she finally realized she had started to shrink, the edge was above her head. She reached up to grab it, and managed to lift her chest up to the edge. She tried to get her fish tail to push off the ground, and though it flopped around a few times, she eventually managed to do it. Her body slipped into the cool water with the faintest of splashes. Her gills sucked water in and out as Mary looked around her in awe. There she was, a half-foot-tall mermaid in a gigantic tub. It seemed more like an swimming pool now, and she didn't even have to breathe underwater!
She did a few laps around the tub, but still wasn't completely satisfied. The water level was only three times her height. She broke the surface and skimmed the water to the vials she had placed on the towel. She looked at the vials and realized they were half her size. If she got any smaller she'd never be able to get the corks off.
She pulled the cork off the Growth vial with some effort and propped it against the wall. Then she took a few more sips of the Shrink vial and propped that against the wall as well.
Slowly the tub enlarged again. Mary dove back into the water and continued to swim, making arcs and twists as she went. The three-inch mermaid dove to the very bottom of the tub, then propelled herself upward as fast as she could. She breached the surface and made a majestic arc in the air.
Mary enjoyed her swim more than anything. She lost herself for hours in the water, swimming, skipping and even simply floating still, delighting in her new form.