When human cells carry out metabolic activities, they will produce carbon dioxide, water, inorganic salts, urea and so on. These metabolic wastes are excreted, which is called excretion. There are three main ways of excretion: the respiratory system exhales gas, the urinary system excretes urine, and the skin excretes sweat. The main pollutants discharged through exhalation are carbon dioxide and a small amount of water, while the main pollutants discharged through urinary system and skin are water, inorganic salts and urea.

So the answer is: excess water in the body is discharged through the skin, urinary system and respiratory system respectively.