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.