Vexed by barnacles, algae, and other wee hitchhikers that attach themselves to the hulls of ships, the maritime industry has been fighting back with a paint that keeps hulls clean for one to five years by slowly releasing biocides that kill off unwanted organisms. Problem is, the critter-killing paint additives don’t stay put — they leach out into seawater where they can damage coral reefs and kill mollusks, seaweed, and other animals and plants. Scientists are searching for new, less destructive strategies to ensure clean ships and smooth sailing. It’s not just a matter of aesthetics; barnacles and other marine life on ships can drive their fuel consumption up by as much as 50 percent, according to the Chamber of Shipping of America.