It is illustrated primarily by Sarah Gibb and published by Orion Children's Books in Britain, and Candlewick Press in America.

[1] The series follows the adventures of thirteen-year-old Emily Windsnap after she discovers that she is half mermaid in the first book and is targeted towards middle grade readers.

Class is going well until Emily dives into the pool and her legs lock together causing her to panic and need to be rescued by her teacher.

Realizing she is Semi-Mer, Emily sets out to discover her family history and find her father.

On the way she makes friends with a teen mermaid named Shona Silkfin who invites her into the merworld under the sea.