Book Review: Deep, by James Nestor

Deep: Freediving, Renegade Science, and What the Ocean Tells Us About Ourselves
by James Nestor
Eamon Dolan/Houghton Mifflin Harcourt, 2014
272pp.
       
This book, like its subject, is breathtaking. Nestor takes us into the world of freedivers, people who go down 100 meters and more with no equipment - and no air.  
Along with following the most dangerous of sports (side note: I would have appreciated a chart or list defining the different disciplines he alludes to), he shows us how this practice came into being as a way to gather food and sponges and to salvage cargo from sunken ships. Nestor visited the handful of living amas, Japanese women who still practice freediving in its ancient form.

Nestor does a good job explaining the physiology involved. Freedivers make use of the mammalian dive reflex, also called the Master Switch of Life (which sounds much cooler) and hone it to incredible levels.  This takes years of training: trying to push one's capabilities too deep, too soon can and does result in death.  As Nestor makes clear, even experienced and careful freedivers take enormous risks.   There is no other sport where blackouts and bleeding from various facial apertures are considered normal. The scariest group of freedivers are the no-limits divers who use weighted sleds to go deep and inflate balloons to rise.  The no-limits record is pushing 215 meters, which was
the maximum rated depth for the Type VII U-boat of World War II.   Nestor takes interesting detours into deep-sea research, including some types enhanced by freediving. Freedivers report that sharks don't bother them and whales accept them to an impressive degree (Nestor doesn't mention that scuba divers, whom freedivers rather look down on, have reported amazing cetacean encounters, too: it's not clear from this book whether there's really a degree of contact unique to freedivers.) He also touches on such interesting subjects as hydrothermal vents, bottom ooze, and privately owned deep-diving submarines: I never knew it was possible to buy a ticket to go down 900 meters in a hand-built sub.  Nestor brings the book to a close on a dive where he finally finds the Master Switch for himself.
As a reader and researcher into marine subjects, I was genuinely sorry to have this book end.