Basically the Octonauts (clues in the name) go to the Hidden World (HTTYD) , a world full of dragons, guarded by a wolf called Camicazi (One of my OCs)

"The middle child has it worse" Janine Margot Doxter knows that this is a lie. Being the younger sister of Dashi and Koshi, who were known as inseparable, mystery-loving sisters in their hometown. Therefore, she has always been the third wheel to her overachieving sisters. Scoffed at for her tomboyish attitude and her love for sports and mischief, she has made herself a reputation as a prankster and a troublemaker. But when the sisters' parents are involved in a terrible accident, Koshi and Jane are put into Dashi's care.