Can drinking too much water cause diarreah? i drank a lot of water on day and also had very watery diarrhea same day.

Yes: When you drink excessive amounts of water, your body can get overwhelmed & more than usual can bypass the stomach & small intestine and end up in the large intestine. The large intestine resorbs water as the stool makes its way around but if there is a huge amount of water, stool content drawing water to stay in the bowel (osmotic pressure), &/or the movement is quick, then you can get diarrhea.