The day starts when the Octonauts watch Dashi taking pictures of a strange underwater cave until Shellington discovers that it's a whale shark's mouth. Dashi gets trapped inside the whale shark as later on the whale shark swallows Captain Barnacles and Kwazii as well while Peso from the outside tries to help the whale shark with a tummyache. Barnacles and Kwazii discover Dashi in the stomach, and they get out to walk toward the mouth, which is closed shut. They were discovering things. In the UK series, this is the very first episode that premiered the show of the Octonauts.