While you're at it, you probably should also research how much water is too much, because on the other side of the spectrum lies hyponatremia and having suboptimal electrolyte levels from overdosing water could be harmful to your cognition too, although I think it's unlikely anyone here will develop a measurable hyponatremia just from drinking too much water. Sweating a lot for example might change the situation.

this definitely seems like something that's worth researching more because it literally affects every single day of your life

This doesn't look like a selective enough heuristic alone.