In this very funny and irresistibly silly junior fiction book, The Bad Guys meet The Treehouse series, but in a brilliantly invented submarine. Readers, be warned! This book is set on Monkey Island and contains a super-smart gorilla called Harold, two regular kids called Poppy and Billy, and the world's greatest inventor, who happens to be their mum. BUT, it also features a villainous kidnapping, a secret volcano, pirates on yachts, a hungry blue whale, exploding basketballs - and a whole lot of water. Plus, there's Mum's greatest invention yet: a Marvellous Submarine.