The exact details of the feeding behaviour of the megamouth shark is unknown, due to the few observations on a live, feeding specimen. The megamouth has a huge mouth that extends behind the eyes. Scientists believe that this shark swims slowly through groups of krill and other small prey with its mouth open, and sucks them in. Then it closes its mouth, and this action decreases the pharyngeal volume and makes it possible for the shark to get rid of any water through the gill openings.