When stranded at sea with no food or water, one might feel the urge to drink the water in the sea. Nonetheless, drinking seawater is a potentially risky activity that potentially might lead to death. Sea water contains high amounts of salt, which the human body is not adapted to process. Hence, consuming it causes a high amount of salt without the human cell, which leads to a steep concentration gradient within the cell, thereby causing water to be drawn out, which is detrimental to the cell.
When one takes in seawater, the high concentration of salt in the water causes the solution outside the cell to be hypertonic. On the other hand, the solution inside the cell membrane is hypotonic. This indicates that compared to the intracellular solute concentration, it has a lower solute concentration (Lopez & Hall, 2022). This causes a concentration gradient between the solution within the cell membrane and that without it. As a result, water moves from the region of low concentration, inside the cell membrane, to a region of high concentration, outside the cell membrane where the sea water is. This is facilitated because the cell membrane is semipermeable, allowing water molecules to flow in and out.
The movement of water from the cell to its environment leads to creation. This is where the cell shrinks due to a lack of water when exposed to a hypertonic solution. This causes the cell to lose its functionality. Further, under normal body functioning, the human kidney usually excretes urine that has a lower salt concentration than seawater. Hence, to excrete the sea salt, the body will need more water, which will cause dehydration, which can lead to nausea, weakness, organ failure, coma, and potentially death.
Reference
Lopez, M. J., & Hall, C. A. (2020). Physiology, Osmosis. StatPearls Publishing.