Captain Barnacles Bear

The leader of the Octonauts. Barnacles is a polar bear who commands every mission the Octonauts perform. Being always the first to help whenever someone is in danger, he is loved by his entire crew, and he loves his crew back.

• Badass Adorable
• Badass Pacifist
• Bears Are Bad News: Averted. He is the nicest and bravest bear you will ever meet. And he is so cute!.
• The Captain
  • The Good Captain
• Fully Dressed Cartoon Animal: The only character on the show to be fully-clothed.
• The Hero
• Ideal Hero
• The Kirk: To Kwazii's McCoy and Peso's Spock.
• The Messiah: Shares this role with Peso. He is very devoted to protecting all sea life.
• Nice Guy
• The Paragon: The Octonaut. He is the leader for a reason.
• Reasonable Authority Figure: He is as fun-loving as the other Octonauts.
• Red Oni, Blue Oni: Blue, to Kwazii's red.
• Super Strength: Strong enough to lift a giant clam.

Kwazii Cat

Barnacles' first lieutenant. Kwazii is an impulsive cat with a mysterious pirate past. He believes in so many different kinds of sea monsters and legendary beasts that he's also considered the crew's cryptozoologist instead of just a lieutenant.

• Badass Adorable
• Berserk Button: When Kwazii's around, you treat Captain Barnacles with respect. Even if you don't know who he is.
• Cute Kitten
• Half-Dressed Cartoon Animal
• Instant Plunder, Just Add Pirates: He is very proud of being a pirate. However, this is also overlaps with The Pirates Who Don't Do Anything.
• The Lancer
• Leeroy Jenkins: In spades.
• The McCoy: To Barnacles' Kirk and Peso's Spock
• Nightmare Fetishist: On the "fascination with creepy things" end of the scale.
• Number Two
• Red Oni, Blue Oni: Very, very red.
• Why Did It Have to Be Snakes?: He is afraid of spiders. Spider crabs are an exception, though.

Peso Penguin

The medical officer of the Octonauts. He is a nice penguin who likes helping people. Peso is a bit shy and can be scared easily, but whenever someone needs help, he is the first to go into action.

• Adorkable
• Badass Pacifist
• Cowardly Lion
• Everything's Better with Penguins
• The Medic
• The Messiah: Shares this role with Barnacles. Peso is one dedicated medic.
• Nice Guy
• The Spock: To Barnacles' Kirk and Kwazii's McCoy.

Professor Inkling Octopus

Professor Inkling, a Dumbo Octopus, is the founder and mentor of the Octonauts. He rarely goes on missions, but his knowledge of marine biology is an asset.

• Bookworm: He likes reading books so much. He practically lives in the Octopod's library.
• Combat Tentacles: Only used once.
• Cool Old Guy
• Everythings Squishier With Cephalopods
• Mr. Exposition
• Non-Action Guy
• The Mentor

Dr. Shellington Sea Otter

The team's marine biologist. Shellington is always there whenever the Octonauts need information about any creature they might encounter in their adventures.

• Adorkable
• As You Know
• Instructional Dialogue
• Dr. Exposition
• Repeating so the Audience Can Hear Tunip's Simlish.
• The Smart Guy: When the Octonauts need information for any kind of creature, he is the go-to guy.
• Voice with an Internet Connection

Tweak Bunny

Tweak is the team's engineer, dedicated to work on special devices to help the Octonauts in their missions or maintain the Octonauts. She is very fond of eating carrots.

• The Engineer
• Righteous Rabbit
• The Smart Girl: She is always there whenever the Octonauts need some special object to complete the mission.
• Wrench Wench

Dashi Daschund

The Octonauts' information officer. Dashi is entrusted with maintaining and controlling the Octopod's computers. She also provides information to the Octonauts in the field. Dashi is a very good photographer and has a collection of cameras and pictures.

• Badass Damsel: While waiting to be rescued from a whale shark's stomach, passes the time by taking interesting photos.
  • Calls for help... lifting a large creature back into the river where it belongs.
• Communications Officer
• Intrepid Reporter: Just watch her report the Iron Clam Competition.
• Nice Girl

Tunip the Vegimal

Tunip is half-vegetable, half-animal creature that serves as the Octopod's cook and gardener. He and his fellow Vegimals are usually seen working to prepare meals for the Octonauts.

• Cheerful Child
• The Cutie
• Fainting: You know that something bad happens whenever Tunip faints.
• Intelligible Unintelligible
• Kid Appeal Character
• Planimal
• Speaking Simlish