The first thing that Linda noticed was a brief sensation of pressure and wetness hitting her on her on the forehead, like the first drop of an oncoming thunderstorm. It was an odd thing to feel indoors and she at first wondered if she'd actually felt it. Then she saw a brief shimmer and watched as it rolled down off her nose and fell on her foot. That got her to look up to the ceiling, it was looking like a decent day was going to start and now she had a leaky roof. Just goddamn great.
Despite this, the plasterwork seemed steadfastly unmarred. Then her attention was brought back downward by two things, a growing sensation of wetness of her left foot and a strange glow. On her sock there was a strange sphere of water about the size of a Golf Ball, ever turning and emitting a faint sea green glow constantly distorted by the shifting surface and smelling of salt.
"What is this?" She said as she poked it with her left hand's pinkie, noticing that it seemed to be expanding. Then the play of lights brought her gaze to her face, which made her scream. The whites of her eyes had turned a deep green while her pupils had become catlike slits. The skin around her eyes was also starting to change. It took on a glossy sheen, became more rubbery and began changing colour. A dark blue mask like patch formed around her eyes while elsewhere it began to turn turquoise. In shock she put her hands to her mouth, only to notice that more changes were happening there as well. Her left hand now had the same dark blue color as her face mask, her nails were becoming claw-like and webbing was spreading between her fingers. The same process was starting on her right. The effected areas all felt ichy and dry, but that was a minor background detail.
"Whats happening to me?" Linda made out quietly as a sloshing sound drew her attention downward. The ball of water had grown to the size of a basketball and it's expansion was now clearly visible. In a panic she tried to recoil and pull her leg free, but whatever it was it had a hold of her and all she accomplished was falling over. As she lay on the floor she noticed that the skin on her left leg was undergoing the same change that her was happening on her hands and face, now having gone up to her knee. Her foot itself felt odd, like it had gone to sleep. Never the less she tried again to break free of it, scrabbling on the floor and pulling on her bed's leg.
As she did so in her thrashing her right foot brushed against the now beach-ball sized sphere. As that happened the water flowed over it and pulled it. This seemed to spur it's grow, making it expand to a meter across in a couple of seconds and just kept growing. At the same time she felt it begin to draw herself in. As she was overcome by the simple force of the water ball she could only think of one thing to say...
"SHIIIIT!"
And with that, she was sucked into the sphere.
She tried to hold her breath as she was dragged beneath the surface, but in the chaos she still swallowed some water. In panic she thrashed about trying to get to the surface, though her hands could never do more than break the surface of the sphere. At first she choked and she figured that this was the end. Then to her suprise the choking subsided and she did not feel out of breath, that brought her attention to an odd sensation by her ribs. She felt about and found six slits growing in the side of her body. She now had gills.
She caught sight of the mirror which had somehow survived unscathed. Nervously, she brought herself to face her it. There she took in what was happening to her. All of her skin had changed color, being milk white on her front and the lower section of her face (save for her turquoise lips) with turquoise with dark green stripes covering the rest. Her hair had similarly become a vivid green. Her nose gradually changed from form into a simple elevated mound while her ears began to regress into her head. When she opened her mouth she saw rows of sharp triangular teeth. To her dismay her blouse and skirt seemed to be disintegrating. Even so, the biggest change was happening lower down on her body.
Her socks had long since crumbled away feet had begun to change shape, her toes were quickly absorbed into the bulk of the appendage, nails dissolving away as the bulk of it became a flatter. All the while her legs were brought together. First it was just like a narrow skirt, but it became more confining and eventually they merged together, first her upper legs then her lower legs and a line of skin moved down. Once it reached the base her feet (which were in no position for bearing any loads anymore) the single column of flesh below her legs began to fill up and round out an a few seconds latter they began moving up, her knees and leg bones shrunk away as this happened and she found that she could thrash what she now could only think of as her tail around from side to side as it grew onward as her spine grew down the tail section. Soon what was once her feet came to rest at the side of her hips and finished their transformation into a pair of tirangular pelvic fins. The last stage of her changes happened as this point as pair of dorsal fins grew from her back just below her shoulders and just above what was her butt and a shark's fluke grew out of the end of her tail. At the same time what was left of her clothes finished their change. She had a bikini top of gold and some sort of white rubbery material and a rough skirt around her waist of the same.
She stared in fascination at her new form. "Oh my god. I'm a mermaid." She said. A bit sharkier than most mermaids she'd seen admittedly, but a mermaid none the less. "How...why?" She also began to notice that things around her began to change. The wood and plaster of her home was turning into some sort of coral, as did her furniture. Her dressers were full of similar bikini tops and skirts. The lamps became some sort of pods attached to the roof. Her alarm clock and computer also shifted into something which had the same shape and function (she was still able to enter her password on the oddly soft keyboard of the now vaguely clamlike affair and log in), but also seemed to be...alive. Various thing in her room like her old doll Susie got (for want of a better word) Mermified.
The last things to change was the door and her window. Both of which became circular affairs about a meter in diameter with sliding doors, with. Both of which then opened and she had the odd sight of watching as they opened and the water began rushing outward, rolling down the hall in a crashing torrent and spilling out of the window like from some giant faucet turned all the way. She expected to be sucked out either way, but oddly enough the water in her room remained mostly still. It was hard to make anything out from beyond the shimmering surface. Soon afterwards she heard crashes presumably as water began expanding outside. A few second latter the entire house was now in a sphere of water thirty meters in diameter and growing steadily at about meters per second.
The world was changing, fortunately she'd changed along with it.