In their fifth thrilling adventure, the explorers journey deep into the Bubble Ocean on their quest to stop the evil Collector, but time is running out . . . The Poison Tentacle Sea was home to the powerful Bone Current.

As they had feared, it gave a sudden surge and pulled them in. Half-mermaid Ursula Jellyfin has always longed for adventure, and this time the stakes are higher than ever.

The Collector is holding a group of children prisoner on Pirate Island, and it's up to Ursula and her friends Jai, Max and Genie to set them free.

Armed with a magical mermaid trident, and with new recruit Zara the pirate fairy on board, their mission is filled with danger.

The explorers must face zombie skeletons, make a daring rescue from a whirlpool and travel through a dinosaur graveyard.

But even if they do make it to Pirate Island, can they fool the Collector and get in to an impenetrable fort?Fast-paced, magical storytelling in a breathtaking underwater world.

Alex Bell's inventiveness and attention to detail is a joy to read. Praise for the series:'A magical adventure of friendship, bravery and derring-do in a richly imagined world.' The Bookseller'A fantastic frosty adventure.' Sunday Express'Wintry, atmospheric, highly imaginative fantasy.' Metro'The most huggable book of the year . . . An (iced) gem.' SFX