Neil Hanson - The Custom of the Sea

There was ample anecdotal evidence to support Tom’s belief. The tales told by the survivors of shipwrecks and passed on in ships’ forecastles and during the long hours of the night watches all had the same conclusion: shipwrecked sailors who drank sea-water experienced delirium, insanity and death.

The sailor then started to drink sea-water and soon became delirious. On one occasion he told me he was going for a walk and went over the side. After a struggle I managed to drag him back into the boat… I struggled with him throughout the night of the eleventh day. By the morning I, too, was becoming weak and delirious and could not restrain the sailor any longer. He went overboard some time on the twelfth day.

Six of the survivors [were] taking occasional drinks of salt water. I warned them they would die a terrible death if they persisted. They obeyed me for a day or two but I soon found them again taking surreptitious drinks of sea-water. As they drank more and more they rapidly became delirious, imagining they could see rivers of water and snow… Three of them jumped overboard shortly after drinking the salt water.

The poor man’s face was a ghastly sight. His eyes protruded straight out of their sockets, while his lips were drawn back over his teeth in a bestial smile. His lips and teeth were covered with a thick white froth. His whole body shook periodically with great convulsions. Suddenly, as three or tour men were trying to hold him down, the man… threw them off and leapt for the side of the boat.

The dangers of drinking sea-water were accepted without question until the early 1950s, when a Frenchman, Dr Alain Bombard, claimed that a castaway who drank small quantities of sea-water from the beginning of his ordeal, rather than waiting until thirst overwhelmed him, could survive. To prove his theory, he set out to cross the North Atlantic in an inflatable boat, L’Hérétique , carrying no supplies of fresh water with him. ‘I had no rainwater for the first twenty-three days… During the whole of that period I proved conclusively that I could quench my thirst from fish and that the sea itself provided the liquid necessary to health… I drank sea-water for fourteen days in all and fish juice for forty-three days. I had conquered the menace of thirst at sea.’

Dr Bombard’s triumphalist conclusion was not entirely accurate. The metabolism of fish allows them to excrete the salt from the food and sea-water they absorb. The fluids Dr Bombard extracted from the fish he caught were enough to dilute the small quantities of sea-water he drank. Had he drunk it on its own, he would not have survived.

Other mariners, including Thor Heyerdahl aboard Kon Tiki and Sir Francis Chichester on Gypsy Moth IV , also drank small amounts of sea-water without ill effect, and other experiments have shown that mixing it with fresh water in a ratio not exceeding five to one is not harmful, but any higher proportion can be fatal.

The old seaman’s superstition that drinking sea-water sends you mad and kills you is absolutely correct. It does so because it dehydrates the body. Sea-water is a concentrated solution of sodium chloride and other salts, and has a higher specific gravity than fresh water. Through a process of osmosis — the tendency of solvents to diffuse through a porous partition, the stomach wall, into a more concentrated solution — water from the rest of the body is drawn into the stomach in an effort to dilute the sea-water.

The body’s response to this dehydration is thirst, stimulating the urge to drink, but if that drink is also sea-water, the downward spiral continues. The sufferer gulps down more and more in a vain effort to slake this raging thirst, but each mouthful only exacerbates the problem. As they become progressively more dehydrated, the cells of the body contract, and shrinkage of the brain cells causes the delusions and insanity. The opposite effect occurs if a child swallows large quantities of chlorinated water after falling into a swimming-pool. It has a lower specific gravity than fresh water and passes through the stomach wall into the body, swelling the brain cells and causing fits in the child.

Although Tom Dudley was unaware of the fact and urged his men to drink their own urine, the urea contained in it has a similar, if lesser dehydrating effect. Despite Dr Bombard’s experiment, unless there is also a sufficient supply of fresh water to dilute it, drinking sea-water or urine will hasten dehydration and death.

When they shared out the next ration of turnip, Tom held his piece in his mouth as long as he could, but most of the moisture had already evaporated from the tin and within a few minutes it felt as rough and dry as pumice. It was all he could do to chew and swallow it.

A lassitude had crept over them all. Their throats were so tight and sore that they barely spoke, staring into the green water, each alone with his thoughts. Towards dusk they ate the last of the first tin of turnips and shared the dribble of viscous, almost congealed fluid in the bottom of the tin. It was a relief when nightfall shrouded the others from Tom’s sight.

Early the next morning, 9 July, Brooks saw a dark shape on the surface, just off their bow. For a moment terror gripped him, certain that the shark had returned to the attack. Then he recognized the shape of the creature and roused the others with a shout. ‘A turtle! To the oars before it dives.’

The turtle was sleeping on the surface, no more than twenty yards off the port side of the boat. A few strokes of the oars brought them within range. Tom gripped the back of Stephens’s shirt as he hung over the side of the boat, his fingers scrabbling for grip on the turtle’s flippers as it struggled to break free.

Stephens lost his hold on the front flipper and threw himself further forward, his head dipping below the surface as he grabbed for it again. Then he straightened up, coughing and gasping, but clinging to the turtle. He dragged it over the side and dropped it on to the bottom boards, where it lay helpless on its back, its flippers waving.

Tom pulled out his knife. ‘We must drink the blood,’ he said. ‘It will do us more good than the meat.’

He picked up the empty tin of turnips, then set it aside and reached for the chronometer case. Stephens held the turtle still as Tom slipped the case under its head and severed its neck with a single slash of his knife. Its struggles in its death throes sent blood pulsing into the metal bowl.

Craning his neck to watch Tom, Brooks had allowed the dinghy to drift beam-on to the waves. The next one broke over the gunwale, flooding the bottom of the boat and filling the chronometer case with sea-water. The men stared at it aghast.

Richard leaned forward. ‘It is only a little water, surely we can drink it still?’

Tom hesitated for a second, then threw it over the side. ‘It is contaminated with sea-water. It will send us mad.’

Stephens stared at the red stain merging with the green water, then rounded on Brooks. ‘If you had minded your work, we, not the fishes, would have been drinking that.’

Brooks clenched his fists and half rose to face him. ‘You mind your words or you’ll be the one feeding the fishes.’

Tom was again stooping over the turtle, catching the last few drops of blood as they dripped from its neck. He did not raise his eyes, but his voice cut through their shouts. ‘You’ll both sit down. Fighting amongst ourselves will only hasten our end.’ He held out the case. ‘There’s little enough. Each man must take only his fair share.’

He handed it first to the boy, then passed it to Stephens and Brooks, and took the last and smallest share himself. There was barely a mouthful of the congealing blood remaining. It was warm, sweet and sickly and hard to force down but he felt a little strength returning almost as soon as he had swallowed it.