Like any other substance consumed in excessive amounts, water can kill you. But before it does, water will get you drunk. This effect is known as water intoxication or hyperhydration.
When you drink too much water, it goes to your brain and it dilutes electrolytes. Electrolytes are solutions that allow electrical signals to travel in you brain. They usually consist of water and another substance like sodium or potassium. When this substance because diluted, they prevent the brain from working properly and eventually cause it to shut down.
Most victims of water intoxication are teens attempting water drinking contests and athletes that over-hydrate. Still, drinking water is important and you need to drink huge amounts in a very short time in order to die. So don’t worry about accidentally hyperhydrating.