The Octonauts - Season 3 (2015)

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Humpback Whale: When a sardine swallows the key to a treasure chest, a humpback whale helps Kwazii track it down. Platypus: While rescuing river creatures after a storm, the Octonauts find a strange egg and come under attack by stinging platypuses.

When a floating garbage patch endangers a flock of pelicans and other sea creatures, the Octonauts and the birds work together to clean it up.

The Octonauts must stop a huge herd of sea pigs before they march blindly into the Mariana Trench - the deepest point on earth.

As Tweak tests the Gup-X deep down in the Midnight Zone, a yeti crab cuts a vital electrical wire in the ship and cuts off all power, endangering itself and the Octonauts.

Shellington and the Vegimals are on a mission to replant a mangrove forest that is put in peril by a school of toothy barracudas.

While rescuing river creatures after a storm, the octonauts find a strange egg.

When Kwazii gets lost at sea aboard the tiny octo-ski, he meets a flotilla of even tinier sea skaters, the only insects of the ocean.

The Octonauts attempt to keep the peace amongst a trio of mudskippers whose home has been flooded.

When Peso's patient, a remora fish, mysteriously disappears, the Octonauts enlist a unique undersea detective - a harbour seal.

An enormous lion's mane jellyfish gets its amazingly long tentacles tangled in the Octopod's engine whilst Tweak is working on it and causes havoc.

Red Rock Crabs: When Shellington and the crew try to gather some skittish crabs who have drifted away from home, they get help from some old friends. Sea Pigs: The Octonauts must stop a huge herd of sea pigs before they march blindly into the Mariana Trench - the deepest point on earth!

Examining a sick sea sponge, Peso is surprised to discover that all sorts of creatures live inside it, treating it like a hotel, a behaviour known as commensalism.

Mudskippers: The Octonauts attempt to keep the peace amongst a trio of mudskippers whose home has been flooded. Immortal Jellyfish: Shellington and the Octonauts try to track an unusual creature: a jellyfish that can transform from old to young repeatedly - and live forever!

Urchin Invasion: The Octonauts head to the kelp forest to visit Shellington's sister, Pearl, and her newborn son Periwinkle - only to find the forest endangered by an infestation of kelp-eating urchins! Lionsmane Jelly: A lionsmane jellyfish gets its long and stingy tentacles tangled in the bubble engine, unintentionally flooding the Octopod and causing havoc.

Pelicans: When a floating garbage patch endangers a flock of pelicans and other sea creatures, the Octonauts and the birds work together to clean it up. Hammerhead Sharks: The Octonauts study a group of baby hammerhead sharks, as they hunt on their own for the first time and poke their noses into trouble.

Sea Sponge: A sea sponge that houses other sea creatures in its pores suffers from a mysterious illness and Peso must figure out the cause. Loggerhead Sea Turtle: When an underwater tremor separates the Gup-X and its crew, Barnacles seeks guidance from a mysterious sea turtle.

When the Octopod goes in for repairs the Octonauts take a vacation, and Peso accompanies Barnacles to help his sister and her new polar cubs learn to navigate the harsh conditions of the frozen arctic.

Tweak has designed a brand-new Deep Sea Station to study the deepest, darkest reaches of the ocean, but the Octonauts face multiple challenges: from getting it down there, to the extreme environment and strange, prehistoric creatures that greet them once they arrive.