An octopus runs on three hearts and blue, copper-based blood

Two octopus hearts pump blood to the gills, and a third pumps it to the rest of the body; that third heart actually stops beating when the animal swims, part of why octopuses prefer crawling. Their blood uses copper-based hemocyanin instead of iron-based hemoglobin to carry oxygen, which turns it blue and makes it more efficient in cold, low-oxygen water.

— Wikipedia contributors, Octopus — Circulatory system, cephalopod physiology