Oceanographer Sylvia Earle was the first person to walk solo on the bottom of the sea, under a quarter mile of water. She has watched humanity’s enduring fascination with “outer space” while she has delighted in “inner space” — the alien and increasingly endangered worlds beneath earth’s waters. These frontiers, as Sylvia Earle points out, are our very life-support system. She takes us inside the knowledge she’s gathered from a lifetime of research and literally swimming with sharks.

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