Water is sometimes called “the universal solvent" because it can dissolve more substances than any other liquid. It can’t break down certain things like oils that well. For living organisms, water is capable of dissolving molecules needed for chemical processes inside of living things. Water being an excellent solvent is important on a biological level. It’s ability to dissolve many different molecules like salts, sugars, acids, etc. means it can help cells use oxygen or move nutrients.
Water also, more specifically, acts as a solvent in the kidney which dissolves substances to help the human body to get rid of it. Since kidneys filter out substances in our bodies, water is very important in the process of dissolving it so it can be released as waste.
During digestion, water is able to dissolve the substances from broken down foods. The nutrients can then be absorbed by our bodies. Many chemical reactions in our bodies take place in water.