An octopus is a mollusk. It has no skeleton. Octopus have the ability to change their skin color and texture, making them one of the most adept creatures at hiding. Because they have no skeleton they can also fit though spaces many times smaller than their body.
Octopus are known to be very intelligent.
They can fit into very small spaces.
Their tentacles are very strong and if one is removed they can grow back.
They have very developed eyesight.
Octopus on glass
Octopus at the Waikiki Aquarium