The Tail of Emily Windsnap by Liz Kessler

Main Character: 12-year-old Emily Windsnap, half-human, half-mermaid
Location: the Ocean
Time period: Contemporary
Genre: J Fiction, Fantasy, Mermaids
Series: Emily Windsnap #1

Despite living on a boat by the ocean's shore, Emily has never learned to swim. More than that, she has never been totally immersed in water--the boat is so small that there's only room for a shower. So she's very excited when she enrolls in swimming lessons. She's a natural in the water--until she feels her legs seize up. Claiming a cramp, she's excused from the rest of the lesson, but she finds herself now afraid to go back into the water. Finally, Emily learns the truth--Emily's father was a merman and Emily will have the form of a human on land but a mermaid in the water.

As it turns out, liasons between merpeople and humans is strictly forbidden by Neptune, King of the Sea. Emily's father has been imprisoned, and her mother's memory of him has been erased. When Emily begins to explore her true nature, she knows she must do whatever she can to bring them back together, even risking Neptune's fury.

This is a very sweet, light fantasy series for young girls.