Ava Blue was abandoned as a baby on the shores of Lake Superior, but was adopted into a loving family. She has been terrified of the water ever since and suffers from severe aquaphobia, a rare medical condition. This is one of the reasons the red-haired Ava doesn’t fit in at her high school. As sophomore year begins, right before her sixteenth birthday, Ava meets a mysterious boy on the dock by her house. As she falls in love with him, Ava is drawn to the water’s edge more and more. Her life begins to change in many ways, including having a much stronger body and a powerful singing voice. After a dangerous incident at her school, a shocked Ava learns from the boy that she is the last surviving member of a great mermaid tribe, and that a war between tribes has begun over her. Everything she's believed about herself and the world is thrown into confusion and chaos.