Season 5 is my idea Season, there are 68 episodes in the season.
Here are the ideas ( There is a movie called The Octonauts Return with this episodes ):
1: The Great Cryptid Search
Release date: June 10 2016
Storyline: Tweak and the Octonauts in the Gup-K goes to meet Ranger Marsh in Australia but they are not going to meet more Invasive Creatures this time, They are going to meet Tweak's mom Flora and other parents of Tweak's Family! When Tweak's mom Asks to find a mythical cryptid, The Bunyip.
2: The Porpoise
Release date: October 29 2016
Storyline: When a young Harbour Porpoise escapes from his pod, The Octonauts find him.
3: The Bull Sharks
Release date: Thursday 5 2016
Storyline: The crew use the gups to rescue some Bull Sharks from a Hurricane.
4: The Salmon
Release date: April 24 2016
Storyline: A Salmon named Dolly sepreated from his upstream and the Octonauts find the upstream.
5: The Loch Ness Monster Legend
Release date: Wednesday 13 2016
Storyline: The Octonauts have an urgent call from Scotland, it was Shellington's Mother Sanda. She said there's a strange long neck in the loch, Could it be the Loch Ness Monster? Or just an unknown Sea Creature?
6: The Clown Fish
Release date: Wednesday 30 2016
Storyline: When hungry Sharks are going to eat Clownfishes for lunch, The Octonauts must rescue the Clownfishes before the Sharks eat them!
7: The Sea Otter Family Mystery
Release date: September 22 2016
Storyline: When Sanda, Shellington, Pearl and Periwinkle are missing, It's a mystery to the Octonauts find them.
8: The Spider Monkeys
Release date: July 10 2016
Storyline: The Octonauts venture in a jungle to find a lost Spider Monkey!
9: The Asian small-clawed Otters
Release date: June 27 2016
Storyline: Shellington and the Octonauts go to visit Pearl's cousins the Asian small-clawed Otters.
10: The Grizzly Bears
Release date: Sunday 12 2016
Storyline: The Octonauts fight with Wolves to protect a 8-year old baby grizzly bear!
11: The 52 Hertz Whale
Release date: April 31 2016
Storyline: The Octonauts invesgate a Mysterious Whale Song in the Pacific Ocean, Can find the Unknown 52 Hertz Whale or die trying?
12: The Box Jellyfish
Release date: Saturday 22 2016
Storyline: The Octonauts must find a safe home to 5 Box Jellyfishes when their home was invaded by Whitetip Sharks.
13: The Ammonite
Storyline: While exploring the seafloor and find sea creatures such as Peale's Dolphins and Royal Grammas, The Octonauts discover an Ammonite fossil.
14: The Transient Orcas
Storyline: When a pod of Transient Orcas invade a Coral Reef, The Octonauts stop them.
15 - The Whale Calf
Storyline: Kwazii and Shellington must babysit Blue Whale calves while their parents look for food.
16: The Little Blue Penguins
Storyline: When a group of Little Blue Penguins get stranded on a King Penguin beach, The Octonauts must get them all back to their regular beach.
17: The Shark Mayhem
Storyline: In Koshi's Birthday, Dashi is teaching her how to surf like an Surfing Snail but a Bull Shark bites Dashi's front leg, Who will surf without being biten?
18: The Pilot Whale
Storyline: The Octonauts help a young pilot whale named Jizzy find his pod as they meet a hungry Mako Shark, some helpful Bend Stick Pipefish and starts being chased by a evil Sand Tiger Shark, Later they find Jizzy's pod.
19: The Hook Island Sea Monster
Storyline: Koshi plays detective again this time to find the Hook Island Sea Monster.
20: The River Otters
Storyline: Kwazii and Captain Barnacles must help Giant River Otters hide from a tidal bore.
21: The Liopleurodon
Storyline: After Sandy's 3rd visit, The Octopod starts being chased by a Liopleurodon and The Octonauts stop the Liopleurodon!
22: The Seal Pup
Storyline: In a vacation on the Beach, Kwazii finds a lost Elephant Seal Pup and the Octonauts must somehow find the pup's Mother.
23: The Megalodon Shark
Storyline: Captain Barnacles, Kwazii and Peso beware of their lifes when the Gup-A is bitten by a Megalodon Shark!
24: The Commerson's Dolphins
Storyline: Shellington and Dashi receive a Dolphin pod Call and rescue a trapped pod of Commerson's Dolphins who were the sounds coming from.
25: The Common Loons
Storyline: The Octonauts need to stop 4 Common Loons who are chasing a storm!
26: The Pacific White Sided Dolphin
Storyline: Koshi and the Octonauts decided to play a game of the Dolphin Ball Event but when they lost the ball, The Octonauts find it with the help of a old friend the Pacific White Sided Dolphin.
27: The Fin Whale
Storyline: Dashi's and Koshi's friend, Abby the fin whale needs to lead a concert in the lagoon but keeps getting distracted so the octonauts have to get her to the concert by sundown.
28: The Hector's Dolphins
Storyline: Dashi's Cousin, Maelyn the Siberian Husky said that the Coral Reef is full of Hector's Dolphins! The Octonauts has to find out where are all the the Coral Reef fish and why did the Hector's Dolphins move from their home to the reef.
29: The Bairdi Crab
Storyline: Maelyn returns with a new pirate themed prosthetic leg for Calico Jack. But when it goes missing, the octonauts have to find out who stole it, and the victim who stole the prosthetic leg turns out to be a thief Bairdi Crab.
30: The King Crabs
Storyline: When a ball of territory King Crabs invade a beach, Shellington and the Octonauts stop them.
31: The Runaway Monster Mystery
Storyline: Pinto returns to the Octopod but to invesgate a Mysterious Creature ( Which turns out to be a Andrew's Beaked Whale ) that stalked Peso during finish watching the meteor showers.
32: The Mahi Mahi
Storyline: Kwazii encounters with a mahi mahi, a rainbow dolphinfish.
33: The Dragonfish
Storyline: Peso must overcome his fear to help an injured dragonfish named Drago.
34: The Monk Seal
Storyline: The Octonauts meet Kwazii's childhood friend, Monty the Monk Seal.
35: The Operation Finderation
Storyline: When Shellington crashes the Gup-O, He finds the Gup-O's new map to how get back to the Octopod and she team up with a Short-Beaked Common Dolphin named Flipper.
36: The Open Ocean Adventure
Storyline: The Octonauts receive an important call from the Open Ocean that it was Peso's grandfather Rubber, he said she needs to find 3 Sea Creatures such as a Shortbill Spearfish, a pod of 8 Pygmy Killer Whales and a Black Footed Albatross, They also rescue sea creatures from Giant Meteor Showers.
37: The Southern Right Whale Dolphins
Storyline: Koshi's friend Mina the Southern Right Whale Dolphin separates from his pod so the Octonauts find the pod.
38: The Goblin Shark
Storyline: The Octonauts discover living fossils in a prehistoric cave including an Goblin Shark.
39: The Puffin
Storyline: Shellington and Barrot find a lost Puffin Chick ( But grows up at the end ) at the beach so The Octonauts look for his mother.
40: The Stonefish
Storyline: Only Kwazii can save the day when a Stonefish stings the whole Octonauts crew!
41: The Minke Whale
Storyline: The Octonauts team up with Kwazii's old friend Annie the Bengal Tiger to help a young Common Minke Whale find his mother.
42: The Zander
Storyline: Dashi, Tweak, and Shellington are in Lake Constance babysitting baby zanders but it gets harder then they thought!
43: The Walking Catfish
Storyline: The Octonauts must rescue Peso's childhood friend Evans the Walking Catfish from wildlifes.
44: The Whalefish
Storyline: Peso and Shellington discover a Whalefish, an incredibly rare deep sea fish!
45: The Garfish
Storyline: A Garfish named Ruggo must overcome his fear of Sharks so The Octonauts help him.
46: The Basking Shark
Storyline: Kwazii is swallowed by a Basking Shark and Peso and Captain Barnacles rescue him.
47: The African Manatees
Storyline: 2 African Manatees are swaped to the shore by a tidal bore near a river and the Octonauts must get them back to the water.
48: The Harp Seal
Storyline: When a baby Harp Seal gets lost, Peso, Shellington and Captain Barnacles get the baby Seal back to his parents.
49: The Mackerel
Storyline: It's Koshi's first day as a detective and the Octonauts join her and her best friends Crickette and Victoria on a mystery to find missing Mackerel babies and get them back to their mother.
50: The Bass Fish
Storyline: Dashi's boyfriend Luke said that the river's Bass are making a journey, The Octonauts watch as their journey begin.
51: The Yellow Tang
Storyline: Koshi's childhood friend Ribbly the Yellow Tang gets lost, somewhere in the ocean and the Octonauts must find him.
52: The Rockhopper Penguins
Storyline: Shellington finds a nest of penguins with Rockhopper Penguin eggs and soon he finds a group of Rockhopper Penguins arriving revealing Shellington entered in their habitat, A tsumani begins leaving Shellington and the Penguins into a island, The eggs are in danger because there are predators ahead.
53: The Hilsa
Storyline: Dashi's Niece, Anna Retriever comes to the octopod with her friend, Jezebel the hilsa saying that she needs a cure after she got sick.
54: The Sawfish
Storyline: Dashi is going to her family reunion in her hometown, California. But it is interrupted by a sawfish.
55: The Beast Fish
Storyline: Kwazii tells a tale about a beast fish but could it be more than just a tall tale?
56: The Candiru
Storyline: Tweak teams up with her cousin, Layla to search for a lost candiru that has short term memory loss.
57: The Peacock
Storyline: Layla and the octonauts try to help a peacock control its aggressive temper after it got stuck in quicksand.
58: The White Swan
Storyline: Anna is trying to react the swan lake for her school play and is helped by a graceful white swan.
59: The Clymene Dolphin
Storyline: Maelyn and Layla have teamed up for a science project about the clymene dolphin. Their dolphin has ran away and they have to work together to find him.
60: The White Sturgeon
Storyline: Captain Barnacles has been kidnapped and Peso can't save him alone so Dashi leads the Octonauts in their spy uniforms to help save their captain from being stung by a sturgeon.
61: The Mako Cave
Storyline: Dashi, Maelyn, Layla, and Tweak discover a cave in a mountain that was hidden for a long time! And they must discover the secret of the cave.
62: The Patagonion Fish
Storyline: The team receives a call from the Arctic tundra. Tracker and Bianca have teamed up to search for a mysterious but not rare fish.
63: The Dangerous Waters
Storyline: The team are in their training uniforms doing a survival test in shark infested waters!