The sea covers seven-tenths of the Earth, but we have mapped only a small percent of it. The sea contains millions of species of animals and plants, but we have identified only a few thousand of them. The sea controls our planet's climate, but we do not really understand how. The sea is still the frontier, and yet it seems so familiar that we sometimes forget how little we know about it. Just as we are poised on the verge of exploiting the sea on an unprecedented scale - mining it, fertilizing it, fishing it out - this book reminds us of how much we have yet to learn. More than that, it chronicles the knowledge explosion that has transformed our view of the sea in just the past few decades and made it a far more interesting and accessible place.