The distinct ‘plough-furrow’ tracks one sees on the sand behind retreating waves are made by Plough Snails. These snails are only found on the southern coast of South Africa. They feed on dead animals washed up on the beach at high tide. To reach the food the Plough Snail extends its foot and lets the tide push it up the beach. As the tide retreats the snail buries itself in the sand to prevent being washed away by the waves or eaten by gulls. As soon as the water level drops the snail heads up the beach again to the high tide mark. They have a preference for stranded bluebottles (Portuguese Man o War) with hundreds of Plough Snails converging on a single washed up colony of bluebottles.