In this fourth explorers adventure we meet Ursula, a part mermaid girl who is determined to follow in Stella's footsteps and help her to defeat the Collector!
Ursula knew the submarine wasn't designed to go this deep, but what choice did they have? No one wanted to get swallowed up by a colossal sneezing jellyfish!

In a distant watery corner of the Explorers Kingdom, a submarine engineer, Ursula, is determined to become an explorer. Unfortunately, she hides an extraordinary secret, which makes her the sworn enemy of the Ocean Squid Explorers' Club were they ever to find out . . . But when The Collector threatens the Club, Ursula throws caution to the wind and leads an expedition through treacherous waters, filled with gremlins, aboard the Blowfish submarine - and joined by her friends Max, Genie and Jai - and even her idol Stella!
Thrilling, heart-pounding adventure with exquisite detail throughout. Alex Bell's world-building is second to none.
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

Alex Bell has published novels and short stories for both adults and young adults including Frozen Charlotte, a Zoella Book Club pick. The Polar Bear Explorers' Club was her first foray into middle grade. She always wanted to be a writer but had several back-up plans. After training as a lawyer, she now works at the Citizens Advice Bureau. Most of her spare time consists of catering to the whims of her Siamese cat.
Tomislav Tomic graduated from the Academy of Fine Arts in Zagreb. He started to publish his illustrations during his college days. He has illustrated a great number of children's books. He lives and works in Zapresic, Croatia.