Did you ever wonder why we’re not supposed to drink sea water? A kidney can’t make urine from a concentration of salts of more than 2%. Seawater is made of 3% salt, so if we drink it, the kidneys have to use existing water from our body to dilute and absorb the extra salt, which in turn makes us even thirstier. This keeps happening until we die of dehydration.
Source: Unbelievable Facts