Polar Bear Male Captain of the Octonauts. He is the strongest member of the Octonauts crew. He has a warm, gentle, and very dependable personality, always thinking of his crew and the animals. His favorite dessert is vanilla pudding. He has claustrophobia due to a childhood accident.

Cat Male Lieutenant of the Octonauts. He is very proactive, energetic, and loves new adventures. Coming from a family of pirates, he is very knowledgeable about all sorts of legendary creatures, though he can be a bit eccentric. He is deathly afraid of spiders. He habitually uses the exclamation "Yeow!" (Shiver me timbers!)

Penguin Male Medic of the Octonauts. He is a bit timid and shy, but braver than anyone when it comes to helping sick or injured animals. He always carries a medical kit and is skilled enough to wrap bandages with great dexterity. He enjoys playing the xylophone and is quite good at it.

Sea Otter Male Marine Biologist of the Octonauts. He is kind and friendly, but a bit clumsy. He has vast knowledge of marine life and gets excited whenever he encounters a new species. He is the only one who can understand the Vegimals' language. His Gup driving skills are terrible, often leading to frequent breakdowns.

Dachshund Female IT and Communications Officer of the Octonauts. She is very cheerful. She loves taking photos, so she always carries her camera and is very attached to it. Along with Tweak, she is tech-savvy and usually pilots the Octopod. She enjoys surfing and is quite skilled at it.

Dumbo Octopus Male Founder of the Octonauts. He is somewhat cynical yet benevolent and kind to everyone. He is the most knowledgeable about marine life in the Octonauts and spends most of his time in the library. He is not very good with machinery. The Octonauts crew members address him respectfully as "Professor."

Rabbit Female Engineer of the Octonauts. She is bright and playful but highly skilled with machinery. She is in charge of all mechanical repairs on the Octopod and builds the Gups and various equipment herself. She has very sharp hearing and twitches her ears to listen better. She has a catchphrase, "Buncha munchy crunchy carrots!"

Vegimal Male Cook and Gardener of the Octonauts. A mysterious creature that is a mix of animal and vegetable, first brought in by Shellington. He has a playful and cheerful personality. He most frequently says the word "Cheepa." He lives with other Vegimals like Codish, Barrot, Grouber, and Tomminnow.