Water is important because it is one of the best solvents in nature. Living systems require solvents in order to mix various chemicals with one another, and water is the best substance for the job. According to Public Broadcasting Systems, living organisms need water because the biochemical processes of life must take place in a fluid.
Water is a good solvent in part because it is a polar molecule. According to WorldofMolecules.com, this means that polar and ionic substances, such as salt, readily dissolve in water. Water's properties as a solvent allow it to promote life because rather than having to transport solid materials, organisms can dissolve metabolites and nutrients in water, allowing them to move more easily through the body. Many organisms use water to flush toxins and poisonous by-products from their bodies as well. Water also facilitates the bending of enzymes, allowing them to produce necessary chemical reactions within the body quickly.
Water is also an important component of temperature control for animals and it is useful for transporting dissolved substances, according to HowStuffWorks.com. Moreover, water is necessary to sustain life on a larger scale as well. It allows humans to grow crops, raise livestock, travel and power factories. Because it exists in solid and gaseous forms as well as liquid, the environment is able to store water as ice and water vapor, making it readily available.