Mary, looking around her cows udder, watches as her new whale tail fills out. Her legs haven't changed as she didn't drink the whole vial. She's only becoming part whale. Her skin has finished changing color and texture. She's a dark blue everywhere except on her belly and chest and around her eyes, which is white.
Pressing her half-hooved fingers over her skin, Mary watches in fascination as she begins to gain weight. Slowly at first, but with increased speed. Whale blubber begins to fill up around her. Once lean, Mary quickly plumps out. Her shapes softens as she grows bigger and fills the tub. Water splashes everywhere.
Mary, now a good way to becoming a whale, with an udder as well, becomes wedged in the tub. She's grown huge! Her arms have filled out and flattened into the general shape of flippers, but still with the mobility and range of a human arm.
Mary then...