Going overboard with water intake poses serious risks, said Dr Elakiya Mathimaran, consultant pulmonologist, VS Group of Hospitals, Chennai. "Overhydration, or water intoxication...occurs when...kidneys can't clear the excess fluid quick enough," she stated. Excess water can cause a sharp drop in sodium levels, called hyponatremia. It can cause bloating, fogginess and nausea, Dr Mathimaran added.