Gender: Male A polar bear. He is the Captain of the Octonauts. He is responsible, kind, and gentle, possessing the greatest physical strength among the crew. He has claustrophobia due to childhood trauma (this is a secret from the crew). He loves pudding and is the one who sounds the Octo-Alert in emergencies.

Gender: Male An Adélie penguin. He is the Octonauts' medic. Though he is timid and easily frightened, he is brave, responsible, and cool-headed when treating patients. He grows more courageous throughout the series and is the smallest character in the Octonauts after the Vegimals. He likes peppermint-flavored seaweed cake.

Gender: Male A ginger-colored cat. He is the Lieutenant (second-in-command) of the Octonauts. He has a playful, sly, brave, and responsible personality. His great-grandfather was a pirate. He loves stories about giant octopuses (the Kraken) living somewhere in the deep sea and ends his sentences with "-meow." He wears a black eyepatch.

Gender: ? A tiny baby octopus. He needs to return to his home in the Caribbean Sea. He stays inside the water-filled fishbowl helmet worn by Peso. He only says "Coba!"

Gender: Female A green rabbit. She is in charge of building and repairing equipment for the Octonauts. She always carries tools on her belt. She is the only crew member who wears a pink headband. She is always eating a carrot.

Gender: Female A dachshund dog. She has a very cheerful and energetic personality. She operates the Octonauts' main computers, and along with Barnacles, she pilots the Octopod. She is in charge of photography and recording marine life.

Gender: Male A sea otter. He is the Octonauts' researcher. He studies marine life and is incredibly kind to babies. He is a doting uncle to his nephew. He is very curious and won't stop until he finds the answer; he has a charmingly clumsy side.

Gender: Male An octopus. He is the founder of the Octonauts and a marine biologist. He is the oldest member of the Octonauts. He is a gentle, elderly professor character who serves as a wise mentor for the team. He is the only one who does not call Barnacles "Captain."

They are the cooks for the Octonauts. They are characterized by only saying "Moo-ba!" They are characters based on turnips.