One very hot day in July, 1943, Lt. (j.g.) George H. Smith of the United States Navy was sitting on a small rubber raft somewhere between Munda and Guadalcanal. He was very thirsty, and he was cursing man’s inability to drink sea water. To his surprise, he saw a booby bird land on the water, put its long neck under the surface, and apparently take a drink.
In Smith’s own words, “It made me mad. I couldn’t understand why the bird, which was only flesh and blood like myself, could drink sea water while I couldn’t.”
Smith’s next reaction was the crucial one. Though under all the strain of a life-and-death predicament, he set himself a plan of scientific investigation.
“I shot the bird,” he relates, “cut him open, and traced the course of the water through his digestive system. Around the intestines of the bird I found a handful of fat, and I reasoned that if I greased my mouth with this fat, I might be able to swallow sea water without tasting it. For five days then I drank a pint of sea water each day.”
Lt. Smith was picked up after 20 days afloat, still in fairly good physical condition.
Smith’s story was widely circulated. His procedure for making sea water drinkable, and the fact that he had drunk a pint of it a day, were even incorporated into survival instructions used by some Navy and Army Air Force crews. Soon, however, less optimistic reactions began to be expressed.
Articles appeared in service publications pointing out that men are not booby birds and that drinking sea water as Smith had done could kill a man. U.S. Navy medical authorities reported that the reason Smith had suffered no ill effects from five continuous days of imbibing sea water was that he was not seriously dehydrated at the beginning of the ordeal and that on the fifth day a rain squall provided him with all the fresh water he could drink. If he had been dehydrated when he started or if the rain squall had not come when it did, he might have lost his life.
Smith himself had noted that the amount of water he lost in urine during the five days was apparently three times the quantity of sea water he drank. Obviously, excretion of the salts in the sea water was taking water from his body, and he would have been dangerously dehydrated if he had continued drinking sea water.
Unfortunately, the medical reports on the incident were not read as widely as the original report, and Smith’s experience is still cited by some survival “experts” as proof that man can survive at sea without fresh water.
Recently several newspapers and magazines of large circulation have carried stories purporting to “prove” that it is safe to drink sea water. Most of these stories are based either on the account of Dr. Alain Bombard, who drifted from the Canaries to Barbados in his raft L’Hérétique in 1952, or on the experiments carried on by the French Navy, which are essentially a continuation of Bombard’s work. The French experimenters now maintain that a man can survive for six days by drinking only sea water. But he must drink it in small quantities—approximately one-tenth of a pint (50 c.c.) at a time. If sea water is to be drunk beyond the sixth day, the French say that the survivor must drink 1000 c.c. (1.05 quarts) of fresh water on the sixth day to help get rid of excess salt.
[pagebreak][media:node/1949 right medium caption horizontal]
In short, it is claimed that the survivor could live for eleven days on little more than one quart of fresh water, although this claim has not been subjected to experiment. Unfortunately, many of the stories written about the French experiments omit any mention of the restrictions on the use of sea water and leave the reader with the impression that the sea will provide all the water a man needs for an indefinite period.
The U.S. Naval Aero-Medical Safety Journal stated in 1955 that “all physiological knowledge at present indicates that sea water is inimical to the human organism and that its use will shorten rather than prolong survival time.” This view has been repeated in other official Navy publications. The U.S. Air Force Manual 64-5 entitled “Survival,” which is carried in all Air Force survival kits and on many commercial airplanes, says: “Do not drink sea water.”
Why do the services take this stand? Is it due to the natural reluctance of medical men to accept a theory that has not been thoroughly tested? Or is it because the theory has been tested and found wanting? The fact is that the problem of providing water for the survivors of shipwreck and aircraft ditchings has been thoroughly investigated, and the investigators have found that the use of sea water is not the answer.
During World War II, the armed forces and the merchant marines of all the combatants were faced with the problem of providing seamen and airmen with a supply of water in case of disaster. This problem posed many questions, the first of which was: How much water does a man need in a survival situation?
The standing rule of thumb used prior to World War II on board naval vessels and merchant ships was “a pint a day per man.” However, tests on subjects placed in a simulated survival situation soon showed that this was not enough to keep a man in water balance. Different investigators came up with different answers as to the exact amount of water needed to prevent dehydration, but all agreed that the minimum amount was a great deal more than a pint a day.
The following table, compiled by Dr. E. F. Adolph and his associates, gives the values generally accepted by the end of the war.
[media:node/1948 large left horizontal]
A team of United States scientists directed by Dr. Adolph went even further and estimated the relationship between total water supply and survival time at various temperatures. Dr. Adolph computed that at environmental temperatures under 70 degrees F., a man who starts out in water balance can survive for ten days. These values apply to an inactive man, in the shade, and with a low calorie intake.
Note that the advocates of drinking sea water claim only that a man can survive for six clays by drinking sea water alone and for eleven days if he drinks slightly over one quart of fresh water while drinking sea water. Thus it appears that by drinking no water at all a man would survive for four days longer as he would on sea water, even if the claims of the advocates of sea rater are valid.
The data for environmental ternperatures of 70 degrees F. and under are used in the example above because all the sea water experiments recorded have been cared out in temperate and cool climates. As is shown in the table below, expected survival time goes down sharply at higher temperatures, even if the subject can remain in the shade.
[media:node/1952 medium caption right horizontal]
The accuracy of Adolph’s predictions has been borne out several times in actual survival incidents. An extensive study of shipwreck survivors during World War II showed that the maximum time without water recorded by any survivor was eleven days—just one day longer than the prediction.
Adolph also demonstrated that, as the body becomes increasingly deficient in water, certain symptoms follow in order. The degree of dehydration was rated by measuring the per cent loss of body weight. At the beginning of dehydration there is thirst and discomfort. Succeeding symptoms, in order, are lassitude, loss of appetite, sleepiness, rise in body temperature and, at about 5 per cent dehydration, nausea. At from 6 to 10 per cent dehydration, the victim will experience dizziness, headache, tingling in the limbs, dry mouth, difficulty in speaking, and inability to walk. At more than 10 per cent dehydration, delirium is common, and the senses fail. Dehydration of 25 per cent is probably fatal at any temperature. At air temperatures above 90 degrees F., 15 per cent dehydration is the theoretical fatal limit.
Yet records of shipwreck survivors show that very few die of dehydration alone. MacDonald Critchley, a British physician who made an extensive study of the factors affecting survival at sea, believes that as dehydration increases, the victim’s will to resist the desire to drink sea water weakens until finally he succumbs to the temptation and death is caused by the ingestion of sea water. Critchley says, “Sea water poisoning must be accounted, after cold, the commonest cause of death in shipwrecked sailors.”
Critchley tells what happens when a very dehydrated person drinks sea water. There is “immediate slaking, followed quite soon by an exacerbation of the thirst, which will require still more copious draughts. The victim then becomes silent and apathetic, with a peculiar fixed and glassy expression in the eyes. The condition of the lips, mouth, and tongue worsens, and a peculiarly offensive odour has been described in the breath. Within an hour or two, delirium sets in, quiet at first but later violent and unrestrained; consciousness is gradually lost; the color of the face changes and froth appears at the corners of the lips. Death may take place quietly: more often it is a noisy termination, and not infrequently the victim goes over the side in his delirium and is lost.”
Those who advocate the drinking of sea water argue that the effects so graphically described by Critehley do not follow when sea water is drunk by a man in water balance. They point out, moreover, that anyone who goes swimming in the sea swallows some sea water and that many castaways swallow substantial amounts of sea water before reaching the safety of a lifeboat or raft. The advocates of sea water maintain that by drinking small quantities of it immediately, a man can both slake his thirst and keep his body in water balance.
The question of whether or not a man can stop or avoid the sensation of thirst by drinking sea water is difficult to prove or disprove. In several experiments on drinking small quantities of sea water, the subjects have reported that they had no feeling of thirst. All these experiments took place in cool climates, and none of them ran for more than six days. In actual survival incidents under similar environmental conditions, survivors who had no water denied any feelings of thirst, and some who drank small amounts of sea water were thirsty.
Actually thirst is only a signal of the body’s need for water. Thirst is often satisfied while the body is still slightly dehydrated. This is especially true in cool climates. Tests made by the U.S. Army in cold climates show that if men drink only when they are thirsty, they stay in a continuously dehydrated state.
The sensation of thirst varies a great deal with individuals. A person’s description of how he feels changes with his psychological as well as his physiological condition, so the term “thirst” can be regarded as little more than an expression of personal opinion. However, the effect of drinking sea water on the body’s water balance can be computed and the computations verified by experiment. It is possible to determine by actual test how much sea water the body can tolerate, though for obvious reasons laboratory experiments cannot carry the study to a point where the subject’s life is actually endangered.
A vital function of the water in our bodies is to permit the kidneys to extract waste products from the blood in the form of urine. The chemical and physical processes involved in this function would take us beyond the scope of a general article. So we are centering our attention on the effect of the ingestion of the dissolved salts in sea water, predominantly sodium chloride or common salt. And the basic point is that the body uses only a very small amount of salt. Additional salt ingested must be excreted with the urine, using water which could be utilized by the body in other functions.
With the osmotic concentration of sea water only slightly below that of urine, the daily pint of sea water that the body will tolerate will only yield about 3/10 of a pint (143 c.c.) of free water for the excretion of other urinary constituents, as Dr. Homer W. Smith points out in his book From Fish to Philosopher. The amount of water actually needed for urine formation is about a pint, not to mention upward of 1500 c.c. more (over 3 pints) for sweat, if the individual is exposed to sun and wind. Yet 500 c.c., or about 1 pint, is the greatest amount of sea water that can be swallowed each day without gastrointestinal disturbance from the unabsorbable magnesium and sulphate. Consuming larger amounts, concludes Dr. Smith, would only lead to diarrhea and further dehydration and would hasten the end.
The most favorable report on the use of sea water is that of W. S. S. Ladell, printed in The Lancet, October 9, 1943. Ladell ran a series of experiments with a group of seventeen men on a “shipwreck ration” such as was carried in lifeboats. Some of the subjects drank sea water, others fresh water or fresh water plus sea water.
Ladell summarized the effects of drinking up to 400 c.c. (a little less than a pint) of sea water daily. The subjects were either totally or partially deprived of fresh water and were on the low-calorie and low-salt diet of the “man on the raft.” Thus they were getting almost all the salt their bodies used from the sea water they drank. Ladell’s conclusions were as follows, both for men drinking only sea water and for those using sea water as an “extender” for an inadequate fresh-water ration:
(a) At first, the subject retains the same amount of chloride that his body had lost before he began to drink sea water. Subsequently he excretes the full amount of chloride taken in. (b) The output of urine is increased, but there is a slight gain in the amount of the water in the body, because the extra water lost in the urine is less than the extra water taken in as sea water. (c) There is a gain in the total urea clearance.
(It should be noted that this experiment was performed in a laboratory where sweating would be at a minimum.)
Ladell’s experiment indicated that a slight advantage was to be gained when a man on limited fresh water or without any fresh water drank small quantities of sea water. However, the agency sponsoring the research did not recommend the drinking of sea water. Evidently it was felt that the small gain to be expected did not warrant the risk involved. Even if the survivor was able to hold his intake of sea water down to the limit recommended by Ladell (400 c.c., or less than 1 pint), the small volume of water gained in this way could not support human life indefinitely and would give little if any extension in survival time over that to be expected by a man drinking no water at all.
The sea-water enthusiasts argue that Dr. Alain Bombard drank sea water and survived; therefore, sea water must be beneficial. What was Bombard’s experience and how does it compare with that of shipwreck survivors? Bombard departed from Las Palmas, Canary Islands, on October 19, 1952, and landed at St. Lucia, Barbados, on December 23, 1952—a journey of 65 days. But 52 days after setting out, he boarded the S.S. Aroka, stayed an hour and a half, and had a meal. These 52 days represent his longest period of survival without outside help.
Bombard’s voyage was a truly remarkable exhibition of fortitude and an impressive demonstration of the capacity of the human body to withstand abuse. However, several shipwreck survivors, less well prepared than Dr. Bombard, have made longer drifts.
The longest drift on record is that of Poon Lim, a native of Hong Kong, who spent 133 days on a raft in the South Atlantic after his ship, the S.S. Ben Lomond, was torpedoed in 1942.
Poon Lim spent the first hour after the torpedoing floating in his life jacket. Then he had the good fortune to reach an unoccupied raft. The raft had food and water for 50 days—but the last 83 days of his drift he subsisted on rain water and fish. Brazilian fishermen picked him up, still in good physical condition after 133 days on his own.
Has the survivor no choice but to rely on rain water as Poon Lim did, or take a chance on sea-water poisoning as Bombard did? Fortunately, most survivors of ditchings or shipwreck will not be limited to these alternatives. Two devices developed during World War II give today’s survivor a margin of safety—the desalting kit and the solar still.
The desalting kit provides a method of converting salt water to fresh in practically any weather, but it can be used only once. The solar still functions only when the sun is shining or under a light cloud cover, but it can be used indefinitely.
The desalting kit precipitates dissolved salts in sea water so that they can be filtered out. Each desalting kit contains a number of briquettes of silver aluminum silicate and a plastic processing bag. Each briquette will desalt about a pint of water. The kit will produce six or seven times as much water as could be carried if the same space were used to carry canned water.
In use, the processing bag is filled with sea water up to a marked line and the briquette dropped in. The bag is kneaded and agitated gently for an hour, allowing the briquette to break up and the chemical reaction to take place. Desalted water is drawn off through a filter in the bottom of the bag, from which it can be drunk directly or squeezed into a storage bag.
The solar still is a spherical plastic envelope that can be inflated either by mouth or by using the pump carried on most life rafts. Inside the sphere is stretched a black cloth, upon which sea water drips from a reservoir. The sun heats the moist black cloth, and from it the water evaporates—fresh. The evaporated fresh water condenses on the inner surface of the plastic sphere in small drops, which run down to the fresh-water trap at the bottom of the still. The salt stays in the black cloth.
Each solar still can produce about two pints of fresh water a day, and most life rafts on aircraft carry several stills. Each still takes up about the same amount of space as a pint of canned water.
The stills operate most efficiently in direct sunlight but will operate on cloudy days if the overcast is not too thick. They will not operate at night or on very dark days.
The map below shows how much help can be expected from rain in various parts of the world. Rain plus the water from the solar stills usually carried on life rafts will usually yield between 80 and 130 per cent of the requirement for survival in almost all areas commonly traversed by planes and ships.
Desalting kits provide an additional supply to carry castaways through periods of unfavorable weather. The inherent ability of the human body to withstand abuse provides a further safety factor.
In view of the resources now available to the castaway, it seems foolish to recommend that a survivor drink sea water. In most emergencies, he will drink some accidentally, and a certain amount of dried salt is also taken in. This unintentional salt would, in most cases, nullify the meager benefit that might be gained from drinking sea water. The drinking of sea water, then, is just another of the recurrent fables that should be given a quiet burial. Man is no more able to drink sea water than Coleridge’s Ancient Mariner.