Barnacles are the only sessile (permanently attached to one location) crustaceans. They were described by the nineteenth-century naturalist Louis Agassiz (1807–1873) as “nothing more than a little shrimplike animal standing on its head in a limestone house and licking food into its mouth.” Accumulations of barnacles may become so great that the speed of a ship may be reduced by up to 40 percent, necessitating dry-docking the ship to remove the barnacles.