Shellington is excited to find the distinctive tooth of a very rare creature, the spade-toothed beaked whale. Now, the Octonauts must find the tooth’s owner, so Shellington can study it, and so that Peso can help replace its tooth. But it won’t be easy: spade-toothed beaked whales like to be left alone and can dive very deep.

The show’s own verdict is on its page.