People imagine the ocean as serene, but the deep has never been the silent world that conservationist Jacques Cousteau once called it. Data suggests most of the 34,200 species of fish can hear, and there’s plenty to listen to. Whales aren’t alone in singing; at least 800 species of fish click, hoot, purr, or moan. A healthy coral reef sounds like corn popping. Storms and earthquakes add to the score. But the industrialization of the sea over the past 70 years has generated enough din to make hearing anything else difficult. For years, few worried about it, because what did it matter in all that water? Yet mounting evidence shows that our racket profoundly impacts marine creatures great and small—​and could shorten their lives.