Neon-hued parrotfish. Graceful angelfish the size of dinner platters. Delicate sponges that sway in the currents. Coral communities teeming with colorful marine life. Our fascination with the oceans and their denizens has led Congress to include within the National Park System some of the nation’s most incredible and beautiful marine ecosystems. Ninety-five percent of Biscayne National Park, for instance, is underwater.