Very good topic. The allowed salinity in our body is 9, which represents the amount of salt in the fluids of our body. Each 1000 grams of fluid, 9 are salt and 991 are water. These fluids are considered isotonic, while sea water is hypertonic because it contains more salt than human blood and its salinity is 35.

Human cells have membranes that prevent salt from freely entering, however they are semipermeable, so a very high salt content in the blood is dangerous. When the salt is outside the cell is greater than inside, the water leaves the cell to balance in a process called osmosis.

When drinking sea water the consequences of osmosis are disastrous. The passage of water to the outside of the cells will cause them to shrink. To remove excess salt from the body, the body will produce urine. However, this liquid may not have the salinity of sea water, so you must urinate much more to remove it, eliminating more water than we drank with salt. In this way dehydration occurs which has deadly effects.