What should i do if i accidentely drink seawater?

Answer 1

Accidentally consuming small quantities of clean seawater is not harmful, especially if the seawater is consumed along with a larger quantity of fresh water. However, consuming seawater to maintain hydration in the long run is counterproductive. In the long run, more water must be expended to eliminate the seawater's salt from the bloodstream (through excretion in urine) than the amount of water that is gained from drinking the seawater itself.

This occurs because the amount of sodium chloride in human blood is actively regulated within a very narrow range of 9 g/L (0.9% by weight) by the kidney. Drinking seawater (which contains about 3.5% ions of dissolved sodium chloride) temporarily increases the concentration of sodium chloride in the blood. This in turn promotes sodium excretion by the kidney, but the sodium concentration of seawater is above the maximum concentrating ability of the human kidney. Eventually with further seawater intake the blood concentration of sodium will rise to toxic levels, removing water from all cells and interfering with nerve conduction ultimately giving seizures and heart arrhythmias which become fatal.

Survival manuals consistently advise against drinking seawater. For example, the book "Medical Aspects of Harsh Environments" (Chapter 29 - Shipboard Medicine) presents a summary of 163 life raft voyages. The risk of death was 39% for those who drank seawater, compared to only 3% for those who did not drink seawater.

Although it is clear that a human cannot survive on seawater alone, some people claim that one can drink up to two cups a day, mixed with fresh water in a 2:3 ratio, without ill effect. The French physician Alain Bombard claimed to have survived an ocean crossing in a small raft using only seawater and other provisions harvested from the ocean, but the veracity of his findings was challenged. In Kon-Tiki, Thor Heyerdahl reported drinking seawater mixed with fresh in a 40/60% ratio. A few years later another adventurer named William Willis claimed to have drunk two cups of seawater and one cup of fresh per day for 70 days without ill effect when he lost his part of his water supply.