Shellington Sea Otter is the Octopod's marine biologist with a Scottish accent. He's a cute, nerdy sea otter who loves doing field research and working in his lab. He's easily distracted by rare plants and animals, but his knowledge of the ocean is a big help in Octonaut missions. He is voiced by Keith Wickham.

Though he may be knowledgeable about marine life, Shellington is a terrible driver and has crashed the GUP-D twice and the GUP-E once. When out on missions, he's usually sitting in the back or in the passenger seat, and for good reason.

Some of his talents include playing the harp, golfing, sleeping during missions, crashing the GUPs, and being humorous.

Just like Tweak, Shellington appears to sleep where he works so his room doubles as the ship's lab. The shelves are filled with many different samples that he has collected while out on missions. This is where he is usually found, viewing samples through his microscope. When not in his room, he is also found in his seat up in the HQ where he assists Dashi with the ship's computers.

In both the original UK version of the show and the US one, Shellington has a Scottish accent.

Shellington has a sister named Pearl and a nephew named Periwinkle. Oddly, unlike his sister and nephew, he wears a helmet while diving, like the other Octonauts. Also, he's allergic to red sea urchins- a delicacy for sea otters.