Highlight from The Secret Language of Ships

What's so bad about shellfish and microorganisms hitching a ride? The crusting of barnacles, mussels, and bacteria—called biofouling—creates drag, slowing ships and upping their fuel intake by as much as 40 percent. Foreign species can also invade ecosystems and outcompete native species for food and space. To remove the hitchhikers, the ship goes into dry dock for scraping or power washing.