Gender: Male Role: Captain Species: Polar Bear Family: Twin sister Bianca, nephew Orson, niece Ursa Features: The reliable captain of the Octonauts. He is incredibly strong and can pilot all Octonaut vehicles with ease. He loves vanilla pudding. He seems to suffer from claustrophobia. Personality: Very kind and brave. He has a warm, gentle, and vast heart like the ocean.

Gender: Male Role: Lieutenant Species: Cat Family: Grandfather Calico Jack, parrot Pete Features: He deeply cares for Captain Barnacles and the other crew members. He has a scar on one of his ears. He has a distinct way of speaking, often adding a playful tone to the end of his sentences. Personality: Playful, mischievous, impulsive, and proactive. He is fearless.

Gender: Male Role: Medic Species: Adélie Penguin Family: Mother, older brother Pogo, younger brother Pinto, cousin Rocco, and numerous family members in the Antarctic. Features: The shortest member of the team. He always carries a first-aid kit and mostly applies bandages, yet everyone always feels better after his treatment. He loves playing the xylophone (and is good at it). While his exact age is unknown, official board books list him as the youngest crew member (excluding the Vegimals). He likes peppermint-flavored kelp cakes. He seems physically weaker than the other members. Personality: Kind and cool, he becomes braver than anyone when an animal is sick or injured. He is very gentle and soft-spoken.

Gender: Female Role: Crew Member (Communications, IT, and Photographer) Species: Dachshund Family: Younger sister Koshi Features: Her technical skills with machinery are top-tier, nearly rivaling Tweak's. She is very popular as one of the few female characters. She loves taking photos. Personality: Very cheerful.

Gender: Male Role: Crew Member (Marine Biologist) Species: Sea Otter Family: Older sister Pearl, nephew Periwinkle Features: He brought the Vegimals to the Octonauts. He has extensive knowledge of marine life. He is clumsy, allergic to sea urchins, and bad with machinery. Personality: A smart bookworm, but often described as being slightly scatterbrained. Usually quiet.

Gender: Female Role: Crew Member (Engineer) Species: Rabbit Family: Father Ranger Marsh Features: In charge of building and repairing all machinery. She loves carrots. Personality: Quite bright and energetic.

Gender: Male Role: Professor (Oceanographer) Species: Dumbo Octopus Family: Cousin Irving, nephew Squirt, and many octopus and squid relatives. Features: The founder of the Octonauts. Like Shellington, he can be a bit clumsy at times. Personality: Quite cynical.

Gender: Male, Female Role: Cooks Species: Fish-Vegetable hybrids Family: All Vegimal siblings; Shellington is effectively their parent as he found and hatched their eggs. Features: Tunip is the leader. Key members include Tunip, Codish, Barrot, Grouber, and Tomminnow. Shellington is the only one who can understand Vegimalese. Personality: All are playful and cheerful creatures.