The most wel-known of the octopus's defense mechanisms is its ability to squirt clouds of ink into the water. Some octopi use this cloud of ink as camouflage; after squirting the ink, the octopus retreats into the ink cloud where the predator cannot see it. Other octopi use the ink cloud as a decoy. If a large. intelligent predator such as a shark knows that octopi use ink clouds for camouflage, it might simply attack the ink cloud blindly, hoping to make contact with the octopus inside. However, some sneaky octopi will release the ink cloud in one direction and scurry away in another direction, leaving the predator with nothing but a mouthful of ink. In addition to confusing predators' sense of sight, these ink clouds also confuse their sense of smell. The ink is composed primarily of melanin(the same chemical that gives human skin its color), which can shut down a predator's sense of smell. If an octopus cannot be seen or smelled, it has a much higher chance of escaping an attack.