Most octopuses are quite safe, but the small blue-ringed octopus is very deadly. The blue-ringed octopus when it feels threatened displays dazzling bright blue rings as a warning. Other octopuses can change colour so they are better camouflaged. They also have an organ called a pen that injects a cloud of black dye in the water as a smoke screen to get away.
Octopuses like eating crabs. They can squeeze their bodies through small holes so they can hide inside rocky chambers. They have excellent vision and have a high intelligence. They can walk using their eight arms with suckers. They can swim backwards by pulsating their arms in and out. They also have a jet propulsion system by squirting water out of their body through a siphon.