The Octonauts and the Decorator Crab  (English, Paperback, Simon, Schuster UK)

The Octonauts follows a team of adventure heroes who dive right into action whenever there is trouble under the sea. In a fleet of amazing aquatic vehicles, the Octonauts explore incredible new underwater worlds, rescue wonderful sea creatures, and often save the day before returning safely home to the Octopod. Under the leadership of Captain Barnacles Bear, closely flanked by Lieutenant Kwazii Cat and Medic Peso Penguin, the Octonauts are always ready to embark on an exciting new mission! The Octonauts and the Decorator Crab When an important object goes missing from their ship, the Octonauts decide stake out the thief. There's lots of tension and a whodunnit feel as more and more pieces of Octokit go missing! The unlikely culprit is finally exposed as a decorator crab, salvaging the crew's things to cover his shell.