Perhaps the closest equivalent to a cat in the ocean is an octopus. They average around the same size as cats, they are known to be playful, they are carnivorous, and they are surprisingly intelligent.

Scientists have trained octopi to perform simple tasks. They have been observed pulling the stoppers out of bottles to get at the stuff inside, and even unscrewing jar lids.

Compared to a cat, the octopus is a weird animal. They have three hearts, all beating in their own rhythm, their blood is blue and they have little concern about losing arms, because they can just grow new ones. Their mental capacity, like cats, is centered in their brains, but each leg also has its own independent brain.

Some of the largest octopi live not in some remote deep part on the Indian Ocean, but in Puget Sound in the State of Washington, USA, where they have been found with armspans up to 30 feet (9.1 meters) long.

On some distant planet with large oceans, octopi may have evolved into the dominant species, in terms of intelligence. Could beings exist somewhere that are better able to communicate, more compassionate, and more successful than humans, that have eight flexible arms and live underwater?

Or, perhaps on some waterworld, their equivalent of octopi would be the pets of that’s world equivalent of humans.

This is a remarkably endearing and educational video. Mark Rober taught us many interesting facts about octopi. The plural can also also be octopuses. He did point out that their blue blood is copper-based, and that they have three hearts. What he didn’t mention is that all three hearts beat with independent rhythms. Among their many defenses, such as camouflage and squirting water out of their jet to swim away very quickly, is the ability to squirt a cloud of ink, thereby obscuring their view from enemies. The largest octopi, living off the coast of Washington State on the west coast of the United States, have been known to grow to beyond 30 feet across (9.1 meters) and weigh as much as 600 pounds (272 kg) Their eyes can be as big as 15 inches (38cm) in diameter.

Similarities:

Eyesight: Both have excellent vision adapted to their environments (cats for hunting, octopuses for detecting movement).

Flexible Bodies: Both can are highly flexible. Cats can twist and contort, while octopuses can squeeze through tiny spaces.

Whisker-Like Sensory Structures: Cats have whiskers, and octopuses have sensitive suckers that detect touch and texture.

Sharp Hunting Tools: Cats have claws, while octopuses have a sharp beak for catching prey.

Sensitive Skin: Both have highly sensitive skin that detects vibrations and temperature changes.

Fast Reflexes: Both react incredibly quickly to threats or prey.

Non-Verbal Communication: Both rely heavily on body language to communicate.

Behavioral & Psychological Similarities:

Intelligence: Both are highly intelligent and capable of problem-solving.

Curiosity: They explore and investigate new objects and environments.

Playfulness: Both enjoy playing, whether it’s with a toy or an object they find interesting.

Solitary Nature: While cats can be social, they often prefer alone time—similar to the mostly solitary octopus.

Ambush Predators: Both prefer sneaky, strategic hunting rather than chasing prey over long distances.

Love of Hiding Spots: Cats love small, enclosed spaces, and octopuses hide in dens.

Night Activity: Many cats are nocturnal or crepuscular, and many octopuses hunt at night.

Escape Artists: Both are notorious for escaping enclosures.

Social & Survival Similarities:

Independent Thinkers: Neither blindly follows orders; they make their own decisions.

Territorial Nature: Both are territorial and defend their space.

Stealthy Movement: They move silently when stalking prey or exploring.

Selective Eating Habits: Both can be picky about their food.

Short Lifespan (Relatively): While housecats live longer than octopuses, neither has an extremely long lifespan in the wild compared to other animals. See Lifespans for lifespans of other animals.

Masters of Observation: Both carefully watch their surroundings before making a move.

Affectionate in Unique Ways: Cats may rub against humans or knead, while octopuses sometimes reach out with their tentacles in a seemingly curious or affectionate manner.