Gender: Male Polar Bear The Captain of the Octonauts. He has a responsible and kind personality. He is gentle yet the strongest member of the Octonauts. Due to childhood trauma, he suffers from claustrophobia (which is a secret from the crew). He likes pudding and is the one who sounds the Octo-Alert in emergencies.

Gender: Male Adélie Penguin The medic of the Octonauts. Although he is timid and easily frightened, he is brave, responsible, and cool-headed when treating patients. He becomes increasingly courageous as the series progresses and is the smallest character in the Octonauts after the Vegimals. He likes peppermint-flavored kelp cakes.

Gender: Male Orange Cat The Lieutenant (Second-in-Command) of the Octonauts. He has a playful, sly, and brave personality with a strong sense of responsibility. His great-grandfather was a pirate. He loves stories about things like a giant octopus (Kraken) living somewhere in the deep sea. He ends his sentences with "-meow." He wears a black eye patch.

Gender: ? A small baby octopus. Needs to return to its home in the Caribbean Sea. It stays inside the water-filled fishbowl hat on Peso's head. It only says "Coba!"

Gender: Female Green Rabbit Responsible for building and repairing the Octonauts' equipment. 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 Dachshund Has a very cheerful and energetic personality. She operates the main computers and, along with Barnacles, pilots the Octopod. She is in charge of photography and recording marine life.

Gender: Male Sea Otter The researcher of the Octonauts. 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 his questions are answered. He has a clumsy side that adds to his charm.

Gender: Male Octopus The founder of the Octonauts and a marine biologist. He is the oldest member of the Octonauts. 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."

The cooks of the Octonauts. They are characterized by only saying "Mooba!" They are characters based on turnips.