A snake tracks its prey using smell, collecting airborne particles with its forked tongue, then passing them to the vomeronasal organ or "Jacobson's organ" in the mouth for examination. The fork in the tongue provides a sort of directional sense of smell and taste simultaneously. The snake's tongue is constantly in motion, sampling particles from the air, ground, and water, analyzing the chemicals found, and determining the presence of prey or predators in the local environment. In water-dwelling snakes, such as the anaconda, the tongue functions efficiently underwater.