Common Octopus
Octopus vulgaris
What you should know
Octopuses are amazing eight-armed animals that live in the ocean and can change their color and shape in seconds to hide from predators. Most octopuses are shy and will squirt a cloud of ink and swim away if they feel threatened. You should never try to grab or pick up a wild octopus, because they can bite and all octopuses carry venom.
Whoa
An octopus has three hearts and blue blood, and each of its eight arms has its own cluster of nerves so the arm can keep reacting and moving on its own even after it is separated from the octopus's body.
Staying safe around it
This one is venomous, which means it can put venom into you with a bite or a sting. Never touch it, and never try to move it yourself.
Always ask a grown-up before you touch any animal or plant. If something bites or stings you, tell an adult right away.
Source: NOAA Ocean Service
Read more about the common octopus at Wikipedia.