Barnacles are a serious problem for the U.S. Navy. A billion-dollar problem. Encrustations of hard foulers—like barnacles and other sea life—are estimated to cost the Navy $56 million per year in maintenance costs and increased fuel consumption for Arleigh Burke-class destroyers alone. That’s topped off with an additional $1 billion price tag for the same class’s 15-year life cycle maintenance, according to estimates by professor Michael Schultz at the U.S. Naval Academy.