Nautiluses are slow-moving predators that feed mainly on shrimp, small fish and crustaceans, which are captured using their tentacles. They only need to eat once a month because they use very little energy to swim. To swim the nautilus draws water into and out of the shell with its funnel, this produces jet propulsion.
Unlike the other Cephalopods, they have an external shell which provides protection and spaces that can be filled with air to adjust their buoyancy. They can withdraw completely into their shells and close the opening with a leathery hood formed from two specially folded tentacles.
Unlike most cephalopods, they do not have good vision although their eye structure is highly developed. Instead of a lens they have a simple "pinhole" eye. Instead they use two special tentacles for the sense of smell to hunt and find mates.