You may have wondered how someone lost at sea could die of dehydration when there is plenty of water keeping them afloat in the ocean. We all know we need water to live, It helps keep our blood pumping, keeps our muscles working, and helps us to metabolize our food. We also depend on salt for much of the same reasons, so it would make sense that a sea of salt water would be fine to drink. This is what many people think, and what ultimately leads to their demise in an emergency situation. So, what if you drink salt water?
Salt water is not safe to drink because salt water is more dehydrating to the body than drinking nothing at all. Humans can only safely consume 9 grams of salt per 1,000 grams of water. We call that number, the salinity of the water, and 9 is same salinity as our blood which is isotonic. In comparison, salt water has a salinity of 35, meaning it has 35 grams of salt per 1,0000 of water, which makes it hypertonic. That means that salt water has almost 4 times more salinity than our bodies.
The cells in our bodies are semipermeable, meaning that sodium (salt), as well as chloride and other substances can get in or out easily, at the rate as water enters and leaves our cells. So when we consume water with a high concentration of salt our cells push water out of our cells to create balance, which is called osmosis. The more water our cells push out the more the cells shrink. We then eliminate the salt from our bodies through our urine, this results in our body losing more water than we are taking in. This results in dehydration.
You may think you’re drinking water, but you are just causing your body to lose water. Soon leg and muscle cramps, dry mouth, and excessive thirst set in then our heart rates increase and our blood vessels constrict, preventing flow to vital organs. You will begin to feel weak and nauseous, and as time passes you will suffer from delirium. As the brain receives less blood flow, a person will fall into a coma and eventually die.
So you you might be asking how sea life survives in salt water. Invertebrates and sea life have the same salinity as their environment, so for sea dwelling creatures, their salinity is a 35 just like the ocean. Also, birds, reptiles, fish, and mammals can control their osmosis with body parts such as gills. This allows fish to drink salt water but they won’t dehydrate.
A human can only go 3 days without water. They call it the ‘Rule of Threes.’ We can live 3 minutes without air, 3 hours without shelter in extreme cold or heat, 3 days without water, and 3 weeks without food. Water is essential because it carries oxygen to our cells while flushing out waste from our bodies. It also cushions joints and without water, we can’t absorb nutrients from food.
Now let’s go back to our lost at sea scenario. You’re floating on a raft in the middle of the ocean. It’s been two days and you’re only still alive because it is not winter or summer, so the temperature is tepid enough for you to survive. However, you are nearing dehydration and feel like you are starving. The sea water is lapping up against the sides of your raft as the sun sparkles off the waves. Your throat is dry and parched, so you give in and cup some water into your hands and drink. For a moment, you feel quenched, but within a minute you need more. So you do it again. In this scenario, you would be dead before day three, faster than if you didn’t drink any of the sea water… what should you do?
Rain water would be safer to drink. If it rains, place clothing items out to absorb the rain water and then ring the shirts into some type of receptacle. If it hasn’t rained, use the sun to generate water. Plastic sweats in heat, so you can use the plastic from the raft, life preservers or anything else you have on board to collect the water.
In summary, do not drink salt water no matter how thirsty you are. It will only speed up your dehydration causing you to perish sooner. If you have food, eat little, because the more you eat the thirstier you will become. You can get away with drinking one teaspoon of salt water every twenty minutes, but be careful in doing this as it can be hard to time if you do not have a watch. If you can time it out, be diligent an and try to go longer than 20 minutes if you can.