The octopus is considered highly intelligent. Octopuses possess a large brain in relation to their size, and they can learn how to do things by watching another octopus. They can use their arms to unscrew jar lids and block the entrance to their dens with rocks. In 2009, scientists at Melbourne's Victoria Museum witnessed an octopus in captivity using a coconut as a piece of armor to protect it -- the first known instance of a invertebrate using an object as a tool.
Many of the octopus species can also change colors and shapes. They can adapt their shape to resemble things such as sea snakes and crabs. Their color is believed to be changed with their emotions.
All octopuses produce venom, but only a few prove deadly to humans. None are aggressive unless removed from the water and provoked. Instead of attacking, they camouflage themselves or use ink to confuse would-be predators. An octopus can also shed one of its arms to distract predators. Over time, the arm will grow back.
Since an octopus has no bones, it can squeeze through the smallest of spaces, which is helpful when escaping from predators. In absence of bones, stiff tendons support the creature's muscles.
All in all, the octopus has some really cool features.