An octopus has three hearts.
Two send blood to the gills. The third sends it around the rest of the body.
An octopus gives each of its two gills a pump of its own. Those two hearts move blood through the gills so it can pick up oxygen from the surrounding water.
The third heart then sends that oxygen-rich blood around the rest of the animal. These separate pumps divide up a job that a single heart handles in humans.