A lost Pilot Fish who eats ocean gunk cleans up the Octonauts' dirty Gups - but he's still hungry! Meanwhile, Captain Barnacles must figure out why a Whitetip Shark is chasing the Gup-A!

What keeps making strange holes in the Octonauts' equipment? Turns out it's a trio of pesky Cookiecutter Sharks, the mosquitoes of the sea! What keeps making strange holes in the Octonauts' equipment?