The family Octopodidae contains the octopuses, a largely benthic group (living on the seafloor). The body is globular, and there are no fins, while the shell has been lost entirely. The mantle edges join to the head, leaving a small opening for the mantle cavity. Octopods, like all cephalopods, swim by jet propulsion; however, they can also crawl over the rocks on the sea floor. The suckers on the tentacles allow the octopus to pull itself along over rocks or anchor itself to the seabed. An octopus usually have a den among rocks or in a crevice from which it leaves periodically to feed.
Unlike the other cephalopods, octopods inject their prey with venom and enzymes. The partially digested tissues are then eaten. Octopods can also use their radula, a rasping tongue-like organ, to drill holes in the shells of gastropods before injecting enzymes. As the occupant is broken down by these enzymes, it becomes detached from the substrate and the octopus can then get to the softer underside of the animal.