The Emily Windsnap series of children's novels features a 12-year-old girl who lives alone with her mother on a boat by the seaside. When Emily takes swimming lessons, she finds out something she did not know about herself. Emily is a semi-mer which means when fully immersed in water she has a mermaid's tail but when she is on land she has human legs. However, her mother appears to remember nothing about mermaids or even Emily's own father. Now Emily and her newly found friend Shona Silkfin embark on a trip through the mermaid realm to find out the truth about her, her father and mother, and the unusual Mr. Beeston, the lighthouse keeper.