Book Review: Deep: Freediving, Renegade Science, and What the Ocean Tells Us about Ourselves

What do we know about the ocean?

That’s the question the book “Deep: Freediving, Renegade Science, and What The Ocean Tells Us About Ourselves” tries to answer. As a journalist, James Nestor was assigned by Outside Magazine to cover the 2011 Individual Depth World Championship. It is arguably the biggest event for those that love freediving which was and still remains an unpopular sport. Fascinated and intrigued by what transpired at the event, the author started to learn more about freediving, the ocean and the fantastic world under the water that we, still to this day, know quite little about.

This book chronicles James’ journey from learning about the beauty as well as horror of freediving to how our body reacts to being hundreds of feet deep in the water, how dolphins & whales communicate and the theory that human life originated from water. James filled the pages with numerous scientific facts and theories, the results of hours of field research that did not lack of danger. Scientific books can be a bit dull, but I found myself glued to the author’s stories, from start to finish. James managed to find a sweet spot where he could be a teacher educating us on science and simultaneously a story teller with an exciting adventure to share.

James would be the first to admit that his book would cover “a sliver of the current research on the ocean”. Yet, I learned a lot from his work and writing. If you want to immerse yourself in the science of freediving and the ocean, have a read. I am sure you’ll learn a thing or two! Here are some of the things I took note

“The term Master Switch of Life was coined by physiologist Per Scholander in 1963. It refers to a variety of physiological reflexes in the brain, lungs, and heart, among other organs, that are triggered the second we put our faces in water. The deeper we dive, the more pronounced the reflexes become, eventually spurring a physical transformation that protects our organs from imploding under the immense underwater pressure and turns us into efficient deep-sea-diving animals. Freedivers can anticipate these switches and exploit them to dive deeper and longer.”

“As it turns out, the tradition of splashing cold water on your face to refresh yourself isn’t just an empty ritual; it provokes a physical change within us.”

“I discovered that we’re more closely connected to the ocean than most people would suspect. We’re born of the ocean. Each of us begins life floating in amniotic fluid that has almost the same makeup as ocean water. Our earliest characteristics are fishlike. The month-old embryo grows fins first, not feet; it is one misfiring gene away from developing fins instead of hands. At the fifth week of a fetus’s development, its heart has two chambers, a characteristic shared by fish. Human blood has a chemical composition startlingly similar to seawater. An infant will reflexively breaststroke when placed underwater and can comfortably hold his breath for about forty seconds, longer than many adults. We lose this ability only when we learn how to walk.”

“At sixty feet down, we are not quite ourselves. The heart beats at half its normal rate. Blood starts rushing from the extremities toward the more critical areas of the body’s core. The lungs shrink to a third of their usual size. The senses numb, and synapses slow. The brain enters a heavily meditative state. Most humans can make it to this depth and feel these changes within their bodies. Some choose to dive deeper.

At three hundred feet, we are profoundly changed. The pressure at these depths is ten times that of the surface. The organs collapse. The heart beats at a quarter of its normal rate, slower than the rate of a person in a coma. Senses disappear. The brain enters a dream state.

At six hundred feet down, the ocean’s pressure—some twenty times that of the surface—is too extreme for most human bodies to withstand. Few freedivers have ever attempted dives to this depth; fewer have survived.”

“If you could take your lungs out of your chest, they are completely flexible and you could blow them to whatever size,” she says, then she puffs up her chest and exhales. What stops the lungs from expanding is the musculature around the ribs, chest, and back. Through stretching and breathing exercises, freedivers develop up to 75 percent more lung capacity than the average person. Nobody actually needs this extra capacity to start freediving, but, like a larger tank of gas, it can help you go deeper and stay under longer.”

“In the water, the deeper we go, the more the pressure increases and the more the air contracts. Seawater is eight hundred times denser than air, so diving down just ten feet causes the same change in air pressure as descending from an altitude of ten thousand feet to sea level. Anything with a flexible surface and air inside it—a basketball, a plastic soda bottle, human lungs—will be at half its original volume 33 feet underwater, a third of its original volume at 66 feet, a quarter at 99 feet, and so on.”

“Three hundred feet is the halfway point to the photic zone. Even in the clearest oceans, with blazing sunlight overhead, visibility at this depth is about .5 percent of what it is at the surface, so the water is perpetually gray and hazy. Without artificial lighting, you can see maybe fifty feet in any direction. Because the light is so diffuse, all directions at –300 feet look the same”

“Getting down to this depth is arduous and often dangerous. Scuba divers can make it to three hundred feet breathing mixed gases, but it takes years of training and is a logistical nightmare. The danger isn’t going down—although that certainly is dangerous—it’s coming back up. For a scuba diver, a one-hour descent to two hundred feet breathing regular compressed air would require a ten-hour ascent to purge the deadly levels of nitrogen gas in the blood that accumulate on the way down. A three-hundred-foot ascent on compressed air would most likely kill you.”

“WHILE NOBODY KNOWS EXACTLY HOW hammerheads, feroxes, and other sharks can navigate in permanently black, deep waters, most marine researchers believe that tiny bumps on the sharks’ heads and the sixth sense of magnetoreception have something to do with it. Called ampullae of Lorenzini, after the Italian anatomist who described them in 1678, these little bumps, which look like tiny freckles along the shark’s nose, are actually pores filled with electrically conductive jelly. At the bottom of each of the roughly fifteen hundred pores is a hair cell that resembles one of the tiny hairs inside a human ear. These cells, called cilia, can pick up the slightest change in electrical fields in the water.”

“Sharks’ electroreceptive senses are remarkably acute. Tests on captive great white sharks have shown that they can sense electrical fields as small as 125 millionths of a volt. Smooth dogfish sharks can detect 2 billionths of a volt, while newborn bonnethead sharks can detect fields less than 1 billionth of a volt.

To put this in perspective, imagine dropping a 1.5-volt battery in the Hudson River in Manhattan and then running a wire from that battery to Portland, Maine, some three hundred and fifty miles away. The dogfish and bonnethead sharks could detect the faint electrical field coming off the wire. This sense is five million times stronger than anything humans can feel. It’s by far the most acute sense yet discovered on the planet.”

“Dolphins and other cetaceans use these clicking sounds as part of a sophisticated form of sonar called echolocation. They’re similar to the clicks sperm whales used to shake Schnöller’s body years ago, only weaker.”

“A simple sonar system, consisting of one speaker and one hydrophone (an underwater microphone), works by first sending out a pulse sound, or ping. That ping travels through water until it hits something, then echoes back. The hydrophone records the echo, and a processor calculates how long it took for the echo of the ping to return. This system can provide information on how far away an object is and the direction it is moving, but nothing more.”

“Dolphins and some whales have the equivalent of thousands, even tens of thousands, of echo-collecting hydrophones built into their heads. When a cetacean sends out a click (its version of a sonar ping), it receives the echo information with a fatty sac located beneath the lower jaw, called a melon. Unlike ears, which provide only two directional sources to gather information, the melon provides the cetacean with thousands of data points. The animal can process these to gauge the distance, shape, depth, interior, and exterior of the objects and creatures around it.”

“In 1958, during one of his first dolphin experiments, Lilly recorded a click-and-whistle conversation between dolphins and played it back at a slower rate. When he adjusted the frequency and speed of these dolphin sounds in water to match human speech in air, he found the ratio worked out to 4.5:1. This was a remarkable discovery. Sound travels 4.5 times faster in water than in air. The frequency of communication the dolphins were using, if modified to the density of water, Lilly wrote, matched the exact frequency of human speech in air. When he played the dolphin sounds at this slower speed, they sounded startlingly similar to human speech. Lilly concluded that dolphins were speaking a language similar to ours, but at a much faster speed, one far too rapid for us to comprehend”

“Sperm whale clicks, which are used for echolocation and communication, can be heard several hundred miles away, and possibly around the globe. Sperm whales are the loudest animals on Earth.

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. They’re so loud that they cannot be heard in air, only in water, which is dense enough to propagate such powerful noises. The noise level in air maxes out at 194 decibels.

Any louder, and sound becomes distorted to the point that it turns from a sound wave into a pressure wave. The threshold of noise in water is 240 decibels; any louder, and the noise will almost literally boil the liquid into vapor in a process called cavitation. Sperm whale clicks could not only blow out human eardrums from hundreds of feet away, but, some scientists estimate, vibrate a human body to death.”