During the course of OBS, our bodies went through many vigorous activities which caused a shift in the way our bodies functioned. That means that our bodies had to work hard to maintain the bodies so that we could carry out body processes and carry on normally.
Water was regulated through the process of homeostasis by our kidneys which maintained water balance in our bodies by controlling the water concentration of blood plasma. Water is usually taken in through eating and drinking and then released through sweating, peeing etc. Producing urine which is of different concentration is vital in maintaining the water balance.
For example, when the water level of our blood plasma is high, lesser water will be absorbed back into our blood stream and our urine will be more diluted. Our bodies had to work harder to keep this balance during OBS since water balance is affected by many various conditions, some of which include the amount of exercise, amount of water drunk, amount of salt intake and the external environment you are in.