Coral Anne Anthozoa is a mermaid princess with two problems: legs. She doesn't allow her genetic deformity to get her down, though. She lives in an airtight house, swims around using a prosthetic tail, and breathes through an air-filtering mouthpiece. Being unable to speak under water, Coral is quiet in social settings, but she's a master of sign language. She spends her days quietly running a center for deaf merchildren.
Coral's fiance Milo (a tall, dark, handsome two-legged doctor) is visiting from the world of "normies" above. She has to introduce him to his parents, play tour guide, plan a wedding, and fight off a big ASSE problem.
The Association for the Submerged Sub-human Extinction (ASSE) is an organization made up of two-legged humans that view merpeople as mutants and who want to wipe-out all of merkind. Coral and her legs are a threat to their mission, because she's a palpable link from merpeople to "normal" people.
Everybody knows that mermaids aren't real--everyone except for merfolk, certain governement officials, underwater contractors, and the odd scuba diver or sailor. Merpeople like it that way. But when Coral is ready to kick some ASSE butt, she may need help (and belief) from the world above in order to save all of mer-kind.
Miss Snark dons her wet suit, straps a tank of extra 02 on the poodle and dives in.
This works because it's funny, turns a trope on it's asse (ha) and makes me want to read more.