Deep: Freediving, Renegade Science, and What the Ocean Tells Us About Ourselves

  • James Nestor
  • Eamon Dolan Houghton Mifflin Harcourt
  • 272 pp.

Attempting to expand our understanding of the oceans, James Nestor explores the practice of freediving and the human threat to our waters.

In the little-known world of freediving (breath hold diving without assistance from breathing equipment), competitors risk death and injury to break records while others freedive to harvest a living from the sea. James Nestor’s excursion into freediving takes him on a non-fiction journey that is part self-exploration, part ocean exploration, and most important, an attempt to understand our connection to the sea.

Nestor tackles these tasks in an interesting and entertaining way, by exploring a variety of ocean activities across the globe and weaving them into related stories. Ultimately he makes some insightful distinctions between competition freediving and freediving as used for other purposes. He describes how humans have gradually lost the incredible freediving abilities that were part of our survival on a water world. Only a few people today may still approach the diving capabilities of long past generations. The book begins at the surface, “0,” and proceeds through successively deeper chapters, each with a mission tied to a depth.

Nestor’s introduction to freediving (Chapter 1, “0”), for both himself and the reader, comes at a world freediving championship in Greece. He is both appalled and intrigued by what he quickly learns is one of the most dangerous sports, characterized by blackouts, ruptured body parts, and extreme tension (mostly in the spectators). Here he introduces the “Master Switch of Life,” a human reaction to immersion in water that triggers physiological responses to facilitate underwater survival. He sets off to learn more.

Along the way, he visits the world’s only undersea human habitat (Aquarius, off the coast of Florida) as he explores the history of human attempts to occupy “inner space.” He discusses coral reef declines and photic zone biology and begins to learn how to freedive, but struggles with the process. Nestor visits the remote island of Réunion where freedivers tag sharks to prevent attacks and he investigates marine animal migration and communication abilities. Then he returns to Greece to view the deepest freedive attempt, to 800 feet, which results in a badly injured diver. It is here where Nestor first draws a distinction between the ego driven competitive diving and the diving of researchers and fishers, who he argues are more in tune with the sea. As a marine researcher, I agree that using the sea is not the same thing as having an emotional connection with it, nor does using it necessarily generate that connection.

The book dives deeper, as Nestor continues honing his freediving skills and also enters the deep sea off Roatan (Honduras) with a dive to 2,500 feet in the home-built, uncertified submersible Idabel. As fascinating as this was, I wished this chapter had more information, which would be justified for that large deep-sea ecosystem. But Nestor moves along, training to freedive, exploring sperm whale ecology off Sri Lanka, and describing how little we know of these deep-diving animals’ complex communications and societies. He continues to his greatest depth, with hadal ecosystems, the expense and hardships of deep-sea science, and the theory that life on Earth may have originated around deep hydrothermal vents. From this theory, Nestor proposes that the deeper we explore, the closer we may come to understanding human origins. The book ends where it started (Greece) with not so surprising news from competitive freediving and a reminder about our connections with the sea.

Nestor’s journey and his efforts to gain proficiency with freediving lead him to conclude that we are running out of time to save the oceans. Throughout the book, he emphasizes that being in tune with the sea puts us in tune with ourselves. This may be true on several levels from an understanding that the sea controls life on this planet to a deeper, emotional connection with the ecosystem from which life originated. There is no question, however, that the planet is changing rapidly, and the sea has the greatest role in these changes. But, it is just as important to recognize the huge part human activity has played in causing global shifts.

The book has a few minor errors that do not substantially detract from its message. At the end of the first chapter Nestor implies humans may “ride thousands of miles deep” and that some renegade researchers have spent more time underwater than anyone else; neither statement is true. The deepest part of the ocean is about 35,800 ft (6.8 statute miles), and many scientists and submariners have spent thousands of hours underwater. Later, he states the mesopelagic is placid and unchanging. That may be true of much deeper regions, but the mesopelgic depths (200-1000 meters) can have considerable physical and biological activity. He also writes that Karl Stanley has spent more time at 1-2,000 feet than anyone else, but again, not so. The pilots and some passengers of the two Johnson-Sea-Link submersibles had thousands of dives to these depths as did many others. The dives off Roatan were not in the Cayman Trench, which is farther to the north and is much too deep for the Idabel submersible.

Overall, this book is entertaining, easy to read, and thought-provoking. At a time when humans sorely need to reconnect to the oceans and appreciate their pivotal role in global health, I recommend this book as one means to begin or continue that process.

Steve Ross is a research professor of marine science at the University of North Carolina at
Wilmington. He has led numerous oceanographic cruises and has spent many hours
underwater using SCUBA gear and research submersibles. Dr. Ross is profiled on
the NOAA Ocean Explorer website

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