Surviving the Extremes: A Doctor's Journey to the Limits of Human Endurance (17 page)

Not more than 25 percent of dietary intake should be from fats. This is no problem for shipwreck survivors. They subsist on fish, which are less than 1 percent fat and have no carbohydrates at all. Fish are food because they are made almost entirely of protein. For a substance to be considered food by the human body, it must contain carbon, the fundamental element of life. For it to be edible, it must also contain hydrogen and oxygen in a form that body enzymes can
break down and recycle. Besides carbohydrates and fats, protein is the only other substance that fits those requirements. But protein also contains nitrogen, making it far more complex than the other two compounds. Adding that fourth element allows for the formation of a variety of building blocks called amino acids, which, depending upon how they link together, endow proteins with an incredible range of properties. Proteins are the basic units of genes, the main components of muscles and bones, and critical parts of hormones, enzymes, antibodies, and tissue-repairing cells. They have some function in every living cell. But as complex as proteins are, they contain a lot of carbon, hydrogen, and oxygen and are still food.

Some protein intake is essential because the nitrogen must be captured and reconfigured to build the human brand of protein. Once the nitrogen is removed, the remainder can be used as fuel. However, too large an intake of protein will tax the body’s ability to process and dispose of it. A normal diet contains about 15 percent protein, but a total seafood diet is close to 100 percent. Because a protein is so complex, it requires five times more energy to break down than a carbohydrate, and the unused nitrogen needs to be highly diluted so that it can pass through the kidneys into the urine. Feeding exclusively on protein forces the body to use up large quantities of energy and water, an especially extravagant process for a hungry and thirsty castaway.

So the supermarket of the seas contains no carbohydrates and few fats, but it does offer an unlimited supply of protein swimming in variously shaped packages around the boat. For the castaway who can catch them, it is not a balanced diet, but it will keep him alive.

After a few weeks, Steve Callahan’s raft looked and smelled like a fish market. Fish were not easy to catch, so when he did get one he was usually pretty hungry. First he cut out and ate the heart and liver—they can’t be preserved, taste the best, and are the most nutritious, especially the liver. Livers are chemical processing factories, filled with vitamins and minerals not present in any other organ. Cutting open the stomach sometimes provided a bonus of partially digested fish, which are edible once the bitter coating of digestive juices has been
washed off. Next Callahan cut the muscles into thin strips, eating some right away since they are easier to swallow while still wet. The rest he suspended on strings hanging down from the canopy. If he didn’t dry them in the sun, they’d spoil within hours. All the inedible parts he collected inside the boat, saving some for bait, not daring to throw the rest overboard until there was a strong current to carry the raft away from the sharks that the food would attract.

The Robertsons and the Baileys fed primarily on turtles. One 80-pound turtle supplies about 20 pounds of protein and 8 pounds of fat, so turtles are a better source of nourishment than fish. Besides the fat, there is always a good chance that the female will be carrying eggs—a much tastier surprise inside than half-digested fish.

Then there were the gifts from above that benefited everyone. Seabirds are attracted to a raft as a place to rest, and all the more so if they smell fish and blood. Once they alight and fold their wings, they can be caught by throwing a cloth or a shirt over them, then killed by suffocating them or twisting their necks. Peeling the skin off is easier than plucking the feathers. Eating them is not a good idea, though, for those who even half believe that seabirds are the wandering spirits of drowned sailors. The birds eat plankton, much of which is bioluminescent. At night, leftover bird parts have been known to glow like ghosts.

Another gift that arrives by air are flying fish, small fish chased at night, often by dolphins. When they sense they are about to lose the race, they jump out of the water and glide through the air, sometimes up to 30 yards, hoping to splash down in a safer spot. It is not unusual, though, that their desperate flight lands them in the bottom of a boat. Putting up a sheet, or some sort of barrier, in the middle of the raft each night greatly increases the odds of waking up to breakfast.

The greatest gift from the sky, however, is rain. A castaway might have all the food he needs, but if he can’t drink, he can’t eat. Most chemical reactions and body functions need to take place in and around water, a throwback to the days when life was lived in the primordial seas. The first chemical reactions of what became biology occurred in water, and though life systems have grown infinitely more complex in the eons since, they have never gotten over their early
origins. Humans may have left the sea, but they took their water with them. Two-thirds of a human body consists of water, distributed throughout every cell. The water is active within each cell and also flows from one cell to another cell, tissue, or organ to facilitate body functions like digestion or circulation. In the process, some of the water is converted to other compounds, or lost outright, as in breathing, sweating, and urinating. With no resupply, a human cannot function beyond five or six days or survive beyond ten or twelve. Rain remains the ultimate source of freshwater for all air-breathing animals. On land, it collects in lakes and rivers. A prisoner on the open sea has to collect it any way he can. A quart a day would be enough to sustain life almost indefinitely, but even that amount may be difficult or even impossible to obtain.

The Robertsons had six thirsts to quench, which they did primarily by catching rainwater in their canopy, used like a tarp to funnel the runoff into containers. Since the canopy was constantly exposed to salt air and to deterioration from the sun, the first “wash” always contained salt and bits of yellow rubber. This spilloff was placed in a separate container so as not to contaminate the water that flowed down after it.

Not wanting to waste a drop, Lynn Robertson, a nurse, came up with the idea of using the undrinkable yellow water as a rehydration enema. Rectums have membranes that extract water—this is how food that has passed through the digestive system is dried into feces. Transoceanic seabirds have a similar membrane in their throats to extract water. When the birds scoop up seawater, the membrane prevents the salt from passing through, so the birds get a drink of fresh water. Reasoning that the contaminated water would be filtered by the rectal membrane, leaving behind the salt and rubber, Lynn connected some rubber tubing to the container and to the bellows pump used to keep the raft inflated, then administered enemas to each of her family members. The teenage boy who was not part of their family refused treatment. Dougal considered ordering him to have it, but decided, on balance, that it was better for him to have less water than to force him to submit to something he found so humiliating that it might crack his spirit. Spirit is critical for survival.

Even without rainfall, humans can traverse the driest deserts if they can find the water hidden below the surface. Oceans also have oases of freshwater—small, mobile collections of drinkable fluid found within the body cavities of fish, turtles, and birds. Sea life can provide at least some water if you know where to look. The blood of freshly killed turtles and birds can be drunk like gravy in the minute or so before it coagulates. An average turtle will yield about 4 cups, if collected under the neck when the artery is severed. Turtle meat and fish fillets also have moisture in them, and it can be extracted before drying by wrapping the pieces in a shirt and then wringing them out. Spinal cords are encased in protective tubes filled with liquid to absorb shock. Snap open a fish’s spine near the tail and there will be a column of watery, sugary cerebrospinal fluid waiting to be sucked out. Eyes, another source, are filled with two transparent liquids, the aqueous and vitreous humors, which allow light to pass through from the lens, or cornea, in the front to the screen, or retina, in the back. Fish eyes can be eaten like grapes, chewing them one by one and spitting out the corneas.

Mining the sea for deposits of freshwater is difficult work, and under a hot sun the amount extracted might well be less than the amount of sweat expended. Castaways keep one eye on the skies, hoping for a bonus of rainfall, but water collection is limited to the capacity of whatever containers are on board. Not knowing when, or if, more rain is coming, they sip their reserves slowly, denying themselves the deep drink that would quench their unrelenting thirst. Then the next heavy rainfall might bring frustration that the containers can’t hold any more—or fear that the storm might sink the boat. Castaways live from rainfall to rainfall, haunted by the fear of both too little and too much. And they have the additional torment of being afraid to drink any of the vast supply of water on which they are floating.

“Water, water everywhere, nor any drop to drink,” said the Ancient Mariner, and the U.S. Army survival manual agrees. Yet many sailors have given in to the temptation to drink seawater. At first they just rinse their mouths with it, then they swallow some “by accident.” It feels good in the throat. They lose control, taking sips, then gulps. Their thirst worsens, compelling them to drink even more. Soon they
become delirious and irrational, and sometimes “go for walks” overboard, providing another example of the sailor’s adage that “seawater sends you mad.” Second only to the effects of prolonged exposure, drinking from the ocean is the most common cause of death in a life raft.

But why should it be? We eat salt all the time, so why is drinking seawater lethal? The answer is that it changes the composition of the blood—a complex chemical mix that is about 1 percent salt, compared with seawater, which is about 3 percent salt. Blood is the only organ that is a liquid, and it flows everywhere, in contact with virtually every cell in the body. Chemical sensors continually monitor its ingredients and are very intolerant of increased salt, whether it comes from seawater, or pretzels, or anything else. Once dissolved in any liquid, salt is very hard to get out. Imagine pouring too much salt into a bowl of soup. The only way to get the taste back to normal is to add water to dilute the concentration. The body works the same way. The kidneys can filter some dissolved salt into the urine, but there is a limit to how much they can remove before they become corroded. As with oversalted soup, the most effective way to get the recipe of blood back to normal is to add water. In the body the process is called osmosis. Whenever sensors in the blood taste too much salt in their soup, they send a signal to the brain that makes you thirsty. This is why bars often put out free salted nuts. You find yourself drinking a second glass of beer, and when your salt content has been sufficiently diluted, you put the glass down.

If the salt concentration of seawater could be reduced to less than 1 percent, any of it that was added to the blood would have the effect of diluting it and quenching thirst. Body sensors would get the blood’s salt concentration back up by pushing water out into the cells, thereby rehydrating the body. Thor Heyerdahl and his crew survived an Atlantic crossing using this principle. They had unknowingly cut the reeds for their raft, the
Ra II,
in the wrong season, when the stalks were not water-resistant. As a result, the raft became waterlogged and sank to surface level. To prevent it from going under entirely, the crew jettisoned a lot of their supplies, including some of the heavy water tanks. This lightened the raft sufficiently for them to continue but left
them short of freshwater. Given that the region of the ocean on which they were sailing was less than 3 percent salt, they added 1 liter of seawater to every 2 liters of freshwater, increasing their water supply by 50 percent—just enough for them to reach South America.

What happens, though, when there are no water tanks, the still is not working, the tarp is dry, even the cans and boots are empty and the rains don’t come? Maintaining 1 percent salt concentration in the blood is a high priority—vital chemical reactions depend on it—so if the body can’t take in water from outside, it will draw upon its own supply, taking it from the cells the blood passes by. Within days, highly sensitive brain cells will demonstrate the effects of drying out as chemical and electrical systems misfire and short-circuit. A person with no water intake at all will lose consciousness in three to four days and die in seven to ten days. A person who drinks seawater will also die within seven to ten days but will remain conscious almost to the end. This is because the body naturally loses a little salt every day. If you limit the amount of seawater drunk to a pint a day, salt buildup will be slow, and body cells will absorb water. After about a week, however, the salt accumulation will overwhelm the kidneys and they will shut down. For a castaway, those extra three or four days of consciousness could be the time needed for fish to collect under the raft or for a passing ship to be signaled.

Whether the ship is there or not, dehydration can lead to vivid hallucinations, my friend and fellow sailor Norman Baker recalled one day as we were served drinks before lunch at The Explorers Club. “The last time I saw a cocktail waitress in a white dress like that was on a raft in the middle of the Atlantic.” Norman was the second-in-command on that
Ra II
expedition that jettisoned most of its water supply to stay afloat. At first Norman’s waitress was just a recurring dream, but one hot, windless afternoon he was on deck dully splicing rope when she suddenly appeared alongside him. She offered him a glass of cold water. He was tempted to take it. He had been at sea forty-three days on a 39-foot raft with a crew of eight men. The only way he was able to resist was to reason that “if she were really there, I would have noticed her before.” Yet for him, she was as real as the thirst and the heat and the isolation. Where had she come from? Norman
may have wanted to believe she had swum aboard in midocean, but he wasn’t irrational, at least not yet. She hadn’t come from the sea; she had come from his mind.