sip water all day...don't chug large amounts. hypernatremia can kill you!
HYPOnatremia occurs from drinking too much water while sweating out the
salt. It results in water intoxication and yes, can kill you but you really have to drink a LOT while taking in no electrolytes. Unless you are running a triathlon and taking in only water, it would be hard to do (though not impossible as we know people do the darnedest things).
Hypernatremia is too much sodium and yes, can kill you, but has nothing to do with drinking water.