It is also possible to overheat, as swimmers doing laps in warm pools and divers sweating into their masks can tell you. A recent Navy study looked at overinsulated divers swimming in cold water and found they needed a bit of heat extraction to prevent overheating. If it were like sea water, you could safely drink sea water, which is not the case. Sea-going birds such as penguins, sea gulls, and albatross can drink sea water. Special glands in their heads excrete excess salt.
Humans have no salt glands.
In humans, kidneys do the main work of regulating body salt levels. If you drank sea water, you would have to get rid of the extra salt because it is just too much for your system. Your kidneys would draw water from your body's supply to dilute the salt to get rid of it, a process so dehydrating that you could die of thirst faster by drinking only sea water than if you didn't drink anything at all. There is no convincing evidence that women are more susceptible to hypothermia than men, as commonly stated by divers. To the contrary, several studies show women may be less susceptible.