When the shadows in the ocean go missing, the Octonauts, a team of eight animal underwater explorers, must travel to the Sea of Shade to find them.

When the Octonauts, a team of eight animal underwater explorers, meet a frowning fish, they try their best to make it smile.

Awakening stranded on a tropical island with no memory of what happened, Aster investigates a secret underwater world to find her missing sister, while Sam connects their disappearance to suspicious events in his own life.

In this story inspired by Jules Verne's "20,000 Leagues Under the Sea," Ana Dakkar, a freshman at Harding-Pencroft Academy, a five-year high school that graduates the best marine scientists, naval warriors, navigators, and underwater explorers in the world, makes astounding discoveries about her heritage and puts her leadership skills to the test against deadly enemies from a rival school.

In the mid-nineteenth century, a French professor and his two companions, trapped aboard a fantastic submarine as prisoners of the deranged Captain Nemo, come face to face with exotic ocean creatures and strange sights hidden from the world above.