When Kwazii discovers a blue whale with an injured tail, the Octonauts attempt to use a giant net and Octofloats to keep it from sinking. Meanwhile, Peso and Tweak collaborate on a special brace for its tail, and Kwazii, Dashi and Shellington try to find it enough food. But when the supporting net breaks, the Octonauts have to launch an emergency free-fall rescue!

After an encounter with a school of migrating tuna, the Octonauts discover that one of the speedy fish, Tina, has been left behind. And she’s injured! Poor Tina has a hook stuck in her mouth and is too weak to swim. After Peso tends to her wound, the Octonauts agree to help get her to the tuna spawning grounds. But they’ll have to be quick: egg-laying season doesn’t last long. Luckily, Tweak’s latest gup, the Gup-R, is the fastest she’s ever built! The Octonauts use it to tow Tina, but when the Gup-R’s battery dies, how will they catch up to the rest of her school?

The gang ventures into a red-hot lava tube to rescue a tiny water bear that does not seem to mind the heat at all.

When the Octonauts go on a pirate treasure hunt, Kwazii meets a Parrotfish.

The Octonauts must evacuate sea creatures before an underwater volcano erupts, but there's one creature that won't budge: a slow moving, gelatinous Blobfish.

When the Octopod breaks down, Tweak and the crew search for a missing part aboard an abandoned prototype of the ship, not realising something lives there.

Captain Barnacles and his crew must catch a runaway Octopod, when it is hijacked by a group of crustaceans trying to escape their algae-infested waters.

When Shellington gets lost in a dark sea cave, he gets unexpected assistance from some blind Remipedes.

When all the Gups go out of control, Barnacles and Kwazii leap onto the backs of some speedy Sailfish to round them up.

The Octonauts must rescue Peso when he gets trapped inside a giant ctenophore.

When Shellington gets trapped in the middle of a massive Jellyfish bloom, it's up to the Octonauts to rescue him.

When the Octonauts all pitch in to help save a sick coral reef, they get some unexpected help from a pod of playful dolphins.

When the Octopod's waterworks are flooded with frightened Humuhumu fish, the Octonauts have to find a way to flush them out.

When a gigantic saltwater crocodile wanders into freezing waters, the Octonauts must figure out how to get the predator back to his warm water home - without anyone getting hurt.

When Kwazii's Gup-B breaks down in a storm, not even brave Captain Barnacles can save him alone. Fortunately, a chain of reef lobsters lends a hand - and some claws.

As a huge storm heads towards the headquarters, the Octonaut crew hurriedly goes into preparation. However, Kwaji, who went out to test drive the expedition ship, is unable to return to Octopold because he is rescuing the animals.

While exploring the Arctic, the Octopod gets trapped in the ice. Only Barnacles's skillful navigation, and the help of a friendly Narwhal, can get them free.

After an underwater tremor, an injured sea cucumber named Slippy gets loose on the Octopod, so to let her breathe, they flood the ship!

The Octonauts must work together as a team to help a lost sardine find her school.

Down in the darkness of the ocean deep, Peso and the Octonauts must help a tiny, injured Dwarf Lantern Shark.

The Octonauts have their hands full as they look after a headstrong young Lemon Shark who's hurt his nose and can't find his way home.

While Kwazii and Peso have their hands full babysitting a bunch of Adelie penguin chicks, Captain Barnacles must rescue the chicks' parents from a perilous sea storm!

Peso must gather all his courage when he travels deep down to the very bottom of the ocean, the Midnight Zone, and encounters the mysterious Vampire Squid.

After a storm, the Octonauts help a female seahorse search for her missing mate. She tells them, to Kwazii's surprise, that the missing male seahorse is about to give birth to baby seahorses!

The Octonauts travel up a treacherous river to help a young migrating eel on her difficult journey.