As Goma-chan is swimming in the river, a shark`s silhouette appears behind him?! The shark turns out to be Dot-chan, a young whale shark that escaped from the local aquarium! Goma-chan and Dot-chan quickly become great friends and have fun swimming in Dot-chan`s tank at the aquarium together. But when Ashibe-kun calls out to Goma-chan that it`s time to go home, Goma-chan doesn`t seem to understand him... What`s happened to Goma-chan?