I thought I might add to Karin’s post.
There are both extremes with drinking too much water or being dehydrated.
Hyponatremia is when there is a decrease concentration of sodium in the blood and hypernatremia is the opposite–an elevated concentration of sodium in the bloodstream.
In hypernatremia water deficits and not salt excesses cause relative sodium levels to rise.
Hope this serves to be insightful.
I agree with Karin. It can also be a concern with endurance athletes, but more because they exercise for such a long duration that they sweat out a lot of additional salt and electrolytes that can not be replaced by water alone. For these athletes, salt tabs or a electrolyte replacement drink are often recommended during endurance training.