They have three hearts, two of which help move their blood beyond their gills. Their third heart’s function is to circulate blood to their organs. The third heart does not beat while an octopus swims, which is part of why swimming exhausts them so much and they prefer to crawl. Octopuses also have blue, copper-based blood, unlike a human’s iron-based blood. This difference in blood type helps octopuses survive in colder waters that have lower amounts of oxygen.