What was the punishment keel hauling?

keelhauling was a punishment which originated from Germany and roughly translated means "to drag along the keel".it is a form of punishment meted out to sailors at sea. The sailor was tied to a rope that looped beneath the vessel, thrown overboard on one side of the ship, and dragged under the ship's keel(underneath the ships hull), either from one side of the ship to the other, or the length of the ship.