By Michael E. Young

The Dallas Morning News

“Deep: Freediving, Renegade Science, and What the Ocean Tells Us About Ourselves” by James Nestor (Houghton Mifflin, 272 pgs., $27)

I grew up within sight of the ocean, close enough to hear the boom of the surf as it exploded across the sandbars. My grandfather pulled his living from the ocean, and a great uncle died in it. I spent thousands of hours in the Atlantic and thousands more along its edges. I knew it, I thought.

Then I read James Nestor’s fascinating new book, “Deep,” an exploration, layer by layer, of the oceans’ depths. My knowledge barely dipped beneath the surface.

Nestor’s journey begins in Greece, on assignment for Outside magazine to cover the 2011 Individual Depth World Championship, the largest gathering of competitive freedivers in the history of this little-known and incredibly dangerous sport.

The aim is to dive as deeply as possible while the increasing pressure of the water squeezes your lungs to the size of fists, your body goes into convulsions and you hallucinate in a dreamlike state. Then, exhausted, you grab a piece of paper with clumsy, unfeeling fingers and start your ascent, praying that you reach the surface before you lose consciousness.

When the competition begins, Nestor follows every movement — the deep breaths, the quick kicks to get below the surface, and then, as gravity gives way, the graceful descents, like skydivers in a different medium. But as divers surface with blood gushing from their noses, or their faces blue from oxygen deprivation, or in the worst cases, are dragged to the surface more dead than alive, Nestor sees only horror in this sport.

Soon, though, he finds another side to freediving, which opens the way to exploring at least this top layer of a whole different world. That leads him on a quest, not just learning to freedive — something that proves enormously difficult until someone suggests he simply close his eyes — but beginning to understand how life can exist and even thrive in the deepest crevices in the sea.

In Honduras, Nestor boards a cramped homemade submarine with its builder, Karl Stanley, and a friend, for a descent that will put them 2,500 feet down.

“The view outside is lunar,” he writes, “boulders, shallow craters and broad, open planes, all glowing as white as if the place has just been dusted with snow.”

Actually, the powdery stuff is calcium and silicon from billions of microscopic skeletons, building up by about an inch every 2,000 years. Life seems impossible here, but as the submarine’s lights show, life is everywhere, just not in a form Nestor had ever seen before.

Later, Nestor takes part in a mission to collect recordings of sperm whales talking — an incredibly elaborate series of clicks that allows the whales to communicate with one another, navigate in the lightless depths where they feed, and identify and “X-ray” anything that passes their way.

“At their maximum level of 236 decibels, these clicks are louder than two thousand pounds of TNT exploding two hundred feet away from you, and much louder than the space shuttle taking off from two hundred and fifty feet away,” Nestor writes. “They’re so loud that they cannot be heard in air, only in water, which is dense enough to propagate such powerful noises.”

In the waters off Sri Lanka, Nestor and a friend have a personal encounter with an adult female sperm whale and her calf, which approach “hissing and blowing steam — two locomotives.”

They pass and seem to disappear before returning to a point about 150 feet away.

“The clicking starts again, louder than before. I instinctively kick toward the whales, but my guide, Hanli Prinsloo, grabs my hand.

“‘Don’t swim, don’t move,’ she whispers. ‘They’re watching us.’

“The clicks now sound like jackhammers on pavement. These are echolocation clicks; the whales are scanning us inside and out. We watch from the surface as they exhale. With a click of their flukes, they lunge toward us.”

The whales come straight toward them until they’re 30 feet away, then pull to the side and veer past.

“They keep their gaze upon us as they pass within a dozen feet of our faces, shower us with clicks, then retreat slowly back into the shadows,” Nestor writes. “The coda clicks turn to echolocation clicks, then the echolocation fades, and the ocean, once again, falls silent.”

Similar scenes unfold throughout “Deep” in what becomes a vivid you-are-there exploration of places few of us will ever visit in a world that none can fully comprehend.

“Deep” is beautiful and terrifying, brutal and hopeful. Nestor pulls us below the surface into a world far beyond imagining and opens our eyes to these unseen places.