These marine organisms cement themselves to submerged surfaces and form dense, rocky colonies. On a ship's hull, they create significant hydrodynamic drag, which reduces speed and drastically increases fuel consumption. Drydock crews must scrape or blast them off during maintenance, and shipbuilders apply toxic or ablative anti-fouling paints to prevent their attachment.
Heard on the job
She's running slow and burning too much heavy fuel, so we need to get her out of the water and scrape the barnacles off.