An octopus cardiovascular system is extremely essential to its survival. This is only because an octopus needs to maintain an extremely high blood pressure to be able to perform certain abilities and tasks. They have numerous strategies for defending themselves against predators, including the expulsion of ink, the use of camouflage and deimatic diplays, their ability to jet quickly through the water, and their ability to hide. This all requires a good amount of oxygen. Invertebrates, they rely on having very high blood pressure in order to move their tentacles. Octopuses have three hearts. The main heart is called the systematic heart, while two smaller hearts pump blood to and from the gills. The two smaller hearts pump blood to the gills, where waste is exchanged for oxygen. The smaller hearts then bring the newly oxygenated blood to the systematic heart.