Author: Liz Kessler
Wow! This is such a good book and also a good series. Emily's dad is a merman, her mom is human, and she is semi-mer (at least that is what they call her) Semi-mer means that when she is on land she has legs and in water a tail. Well lets move on...
Emily is a perky kid who enjoys being a mermaid, although her mother seems to be having a difficult time reconciling the fact that Emily's more academic studies have been put aside for her mermaid studies, oceanography and underwater hairstyling. The ever-widening chasm between the lives she shares with each of her parents starts to cause a rift between them, and Emily fears they will break up.
But then King Neptune, still angered from the loss of his only true marriage with a human, learns that Emily has uncovered the diamond ring which he gave his beloved decades before. He had hoped it would never find its way to the surface again. As a result, he decides to ban marriage between merpeople and humans and curses the offspring of such unions. Emily is forced to become either fully human or a complete sea creature, ensuring that one of her parents would be lost to her forever, and from there it just gets better.