I decided to get rid of my previous opening, which was more of a prologue, and jump right into the story. It's completely different, and I welcome any new suggestions:
There was a thud as Ondine dismounted her manta ray and landed solidly on the sea bed. The jolt it sent from her prosthetics into what remained of her thighs made her long for the days when she was weightless.
After tying the ray to a post in Proteus Square, she noticed that the strap binding the left prosthetic to her stump had come loose again. She pulled harder this time, making it as tight as she could.
Until it hurts, Aegir told her. And even after two years, it did hurt, every time.
Once the strap was secure and causing a sufficient amount of pain, she walked around her manta ray, gently skimming her fingers over the long scar that crossed the creature’s belly. She came to a stop once she could see into one of the ray’s eyes.
“Stay here, Farrow. You won’t like where I’m going.”
Farrow see-sawed in protest, but Ondine gave her a reassuring pat on the fin.
“It’ll be all right. I’ll be back before you know it.”
She hadn’t walked five steps before she started attracting attention, but that was because Seafolk don’t walk. Their muscular legs, hind-fins, and webbed toes made them natural swimmers.
Ondine’s legs, however, were forged in the thermal vents below Aegir’s workshop.
As each metallic footfall drew more eyes her way, her hand drifted to the rapier at her side. They would all know who she was; there were few in the kingdom who hadn’t heard of the king’s second daughter, who was half-machine.
Ok, so this is 256 words. Sue me (please don't).