"Deep" by James Nestor

I had never heard of freediving before reading this book.  Apparently it is the sport or spirituality--depends who you ask!--of diving deep in the water without gear.  There are no scuba masks or oxygen tanks.  All divers rely on is their breath, and some can hold theirs for upwards of fifteen minutes while diving to depths of 300+ feet below the surface!  Nestor goes into the science of how freediving works and how one can learn to extend their capacity to hold their breath.  There are also special techniques for alleviating pressure in one's body since the deeper one swims in the ocean the more intense the pressure becomes.  Nestor shares the frightening accounts of people who have taken freediving too far in attempts to set world records--some have becoming permanently paralyzed, some suffered brain damage, and some even died.  Alongside the fascinating field of freediving, Nestor also elaborates on much of the cutting edge science surrounding sea creatures.  Since many free divers interact with wildlife, a few have actually started their own research.  Readers go with Nestor as he explores underwater submarines, hears dolphin clicks, and swims with whales.  Overall I learned a lot from this book and it has renewed my interest in the ocean.