In this spirited and engaging book, science writer Kunzig, an editor at Discover magazine, voyages among oceanographers, alive and departed, from dockside to textbook, and reports back on our current understanding, and often dubious treatment, of the world’s oceans. Seventy percent of our world is hidden by the oceans’ surface. The often great depths precluded serious study until recently, when sonar and probes and submersibles started to take its measure. Far from the barren wastes it was thought to comprise, Kunzig makes clear, the ocean is an unfathomably rich place, even in the cold, lightless crushing deep, where the diversity of species rivals that of a tropical rainforest. Kunzig starts by bringing readers up to speed on oceanographic thinking. For instance: no, the oceans were not formed by volcanoes, but rather by a torrent of planetoids that pelted Earth and kicked up blankets of steam. He goes on to profile scientists and their seminal work, from Henry Cavendish, the egghead archetype who discovered the composition of water, to the toilers in the oceanic trenches at Columbia University’s Lamont-Doherty Earth Observatory. He describes the wild denizens of the deep sea (porcelain-white crabs, the utterly bizarre sea cucumber), abyssal storms, the sea floor’s endless quadrille. He delivers a Cook’s tour of seawater in global circulation, forgives the lax morals of water molecules as they change partners billions of times a second. And Kunzig strikes a number of cautionary notes. Poised as humans are to exploit the ocean to its max, it would be wise to remember our boundless ignorance as to its workings. We have nearly fished cod to extinction, a fish once so plentiful that Vikings could practically use them as cobblestones from the Faroes to Newfoundland. A nimble, thorough introduction to the ocean in all its vast, untamable, and fearsome attraction. Kunzig’s flair should stir readers’ awe and allow them to share in his protective urge.