Mermaid princess Lily is about to renounce her place in the royal succession of the undersea kingdom of Thalassina and spend her life on land with the boy she loves, until her annoying cousin appears and throws her decision into doubt.
Seventeen-year-old Lily, half-mermaid and half-human, has been living on land and attending high school, where she develops a crush on a boy but is afraid to tell him of her true destiny as the ruler of the undersea kingdom of Thalassinia.