@justin_danger_nunley: Octopuses actually have three hearts: two branchial hearts that pump blood through the gills, and one main systemic heart that circulates that oxygen-rich blood to the rest of the body. The main systemic heart temporarily stops beating every time the octopus swims. Because the blood stops circulating efficiently while they swim, it exhausts them quickly. This biological limitation is exactly why they strongly prefer to crawl along the ocean floor rather than swim.