The Coast Guard tackles everything from dangerous rescue missions to nasty oil spill clean-ups, earning guardsmen the playful nickname “duck scrubbers.” But ocean conservationist David Helvarg says the Coast Guard’s environmental duties are vastly important to marine life and underappreciated in the U.S. military. Helvarg talks with host Jeff Young about his new book, “Rescue Warriors: The U.S. Coast Guard: America’s Forgotten Heroes.”