The octopus is basically a head with arms! The octopus has eight arms, and moves by crawling or swimming. Its body has no bones or outer shell; it is mostly soft. Octopuses can be many different sizes. The largest can be up to 30 feet long and more than 100 pounds and the smallest can only be one inch long.
The octopus has three hearts; two that pump blood through the gills and one that pumps blood through the body. The octopus has a good brain and scientists view it as being a very smart animal!
The octopus also has very good eyesight but does not seem to be able to see colors. It uses its suction cups to taste creatures by touch first, to see if it likes it as food or not. The octopus has a mouth that is more like a beak. It likes to eat clams, lobsters, and many other shelled creatures.
The octopus mostly uses three ways to defend itself against other animals that want to eat it. First, it can hide by changing its skin color to match the rocks and plants around it. Second, it can leave a cloud of black ink-like liquid that can help it get away because the other animal cannot see it. This cloud also messes up the smell of some animals like sharks, which rely on smell to hunt the octopus. Third, it can fit into small cracks where it cannot be reached and eaten.
There are more than 150 different types of octopus. Some live in deep water and others live in shallow. Most live in water near warmer places (tropical or subtropical). Some also live in coral reefs. The octopus lives in a den by itself.