Every now and again, I like to pick up a book on something I’m curious about. This time it was James Nestor’s book titled ‘Deep’ about a sport I find fascinating, freediving.
Freedivers go down upto 200-300 feet on a single breath of air and stay down for 4-5 minutes. This sounded incredible and I wanted to find out more.
The book starts with competitive free diving which is the second most dangerous sport after base jumping, and for good reason. But that is not the essence of what freediving is.
Our bodies in the water are transformed by something called ‘mammalian dive reflex’ or the master switch of life. A series of physiological changes take place in our brain, lungs, heart and other organs, the moment we put our faces in water. The deeper we dive, the more pronounced are these reflexes, which protects our organs from the immense pressure under water. For example, elite divers have their heart rate slow down to 7 beats per second, thereby needing far less oxygen than on land. Under normal conditions humans have a blood-oxygen saturation of 98-100 percent. Few healthy people will ever go below 95 percent, and yet elite free divers have recorded blood-oxygen saturation at 40 percent while maintaining mental and physical acuity. Ancient cultures used the master switch to harvest sponge, pearls, coral and food by diving hundreds of feet for as long as fifteen minutes at a time. This is a skill that modern humans can reclaim through practice.
The author explores our own origins from the ocean through the similarities between humans and life forms in the deepest waters. We begin life in an amniotic fluid which has almost the same make up as sea water. Apparently, the one-month-old human embryo grows Fin-like structures before they develops into feet. At five weeks, a fetus’s heart has two chambers, a characteristic shared with fish. Infants will reflexively swim breaststroke when held in water and can hold their breath easily for forty seconds, longer than many adults.
Freediving is used by researchers to study marine ecosystems in a way that was not possible using scuba or robotic vehicles. The book is packed with little known facts about the ocean and its inhabitants. Consider this, Dolphins use their name signatures when they approach other dolphins, to identify themselves. They also speak their names when they approach humans. The frequency of communication dolphins use in water, matches the frequency of human speech, when we account for the density of the water. Marine mammals like dolphins and whales may also use a form of visual language called holographic communication. This is similar to us exchanging photos on smartphones!
The book made me reflect on our place in the world, through an activity with deep roots in our shared past. A skill that is available to anyone willing to undergo the initial discomfort of going without breathing for manageable lengths. It laid bare our assumptions of what is logical and what we consider possible. We are alive at the edge of our comfort and ability, all else is mere existence.
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