Octopus and Squid use their ink as a defense mechanism to escape from prey. When feeling threatened, they can release large amounts of ink into the water using their siphon. This ink creates a dark cloud that can obscure the predator's view so the cephalopod can jet away quickly. The ink also can contain a compound known as tyrosinase, which irritates the predator’s eyes and paralyzes their sense of smell temporarily.

Source: CIMI