Kingdom Under the Sea (Book 7) Fairy Unicorn Series

Zoe and Astra are together again on magical Unicorn Island, and this time they're on an adventure to the Kingdom Under the Sea, where the sea unicorns live, to try and find a precious spellbook. They know it's hidden at the bottom of the ocean in Sea Dragon Cave. They're sure they'll be able to retrieve the spellbook, as the dragon isn't real - it's just made of stone... or is it?

Series: Fairy Unicorns
Zoe is staying with her Great Aunt May for summer vacation when she discovers a secret world, a land full of Fairy Unicorns, but Zoe soon finds out that Unicorn Island is in terrible danger.