Inkjet. Octopus is a creature that lives in the ocean. They are smart and have many ways to protect themselves. In addition to changing color, they can also spray ink when they are in danger. The main purpose of ink-jet juice is not to resist the enemy's sight. Marine creatures such as fish have a keen sense of smell and hearing, and they mainly use these two senses when hunting. The main purpose of octopus inkjet is to paralyze the enemy's sense of smell, so as to achieve the purpose of protecting themselves. There is a part of octopus's body called ink sac, which can store ink. When they are in danger, they will actively shrink the ink sac and release the ink.