It is Marnie Blue's first day at Mermaid School, and she's worried. What if she can't make any friends? Or has to ride a seahorse? And what will the teachers think when they find out that her aunt is Christabel Blue, the famous singer and DJ but also the naughtiest mermaid in the school's history?
Marnie's determined to make a good impression, but the Blue family are never far away from trouble ...