Male polar bear beast-kin. The leader and Captain of the Octonauts. He wears a blue captain's hat and a blue uniform-style wetsuit, with an Octo-compass at his waist. His favorite dessert is vanilla pudding. He suffers from claustrophobia due to a childhood accident. He is the strongest and most respected member of the crew. He has a gentle, warm personality and cares deeply for his crew. He is skilled at playing the accordion. He likes orcas. He has been stung by a jellyfish before. In the past, his Gup was struck by lightning, he had an arm caught by a giant clam, and he was attacked by barracudas before falling off a blue whale's back into a shipwreck. He once had to hold his breath and swim to his Gup when his air ran out. (His survival skills are that high.)

Male orange tabby cat beast-kin. He usually wears a black eyepatch for style. His personality is playful and mischievous, but he cares for Barnacles and the crew. He has quick judgment and is the second strongest after Barnacles. He has a scar on one ear and comes from a family of pirates. When Kwazii is surprised, he says, "Shiver me timbers!" When he sees a new sea creature, he makes up fake theories to scare Peso. He is agile and light on his feet. He seems fearless but is actually quite a scaredy-cat and really hates spiders. He likes cocoa. He is quite sensitive to the cold. He is good at table tennis.

Male penguin beast-kin. He is timid and easily frightened, but he still has a bit of courage. He always carries a small medical kit. It usually contains bandages, a stethoscope, and so on. He is very good at applying bandages. He is skilled at playing the xylophone. He is quite weak compared to the other crew members.

Male sea otter beast-kin. A model student, researcher, and bookworm (doesn't wear glasses). He has a sea urchin allergy. He is bad at driving the Gups.

Female Dachshund beast-kin. A photographer in charge of communications and information technology. She usually carries a camera and is good at surfing.

Male Dumbo octopus beast-kin. An oceanographer and the founder of the Octonauts. The oldest member of the Octonauts. He is usually addressed as "Professor Inkling." He mostly stays in a chair or moves around in a mobile chair. He is usually found in the library.

Female rabbit beast-kin. An engineer in charge of building and repairing all machinery on the Octopod. Tweak's catchphrases include "Munchin' munchin' carrots!", "In a heartbeat," and "Right away, Cap!"

Genderless and mainly in charge of farming or cooking. They can speak, but it's unintelligible. Shellington is the only one who can interpret it.