Water has importance inside cells and externally. This may be because it has interesting chemical and physical properties; it can be found naturally in all three of its states. However its molecules are bonded together by hydrogen bonds, this raises its melting and boiling points, i.e. its boiling point would be -120?é?ó?é?¬C rather than 100?é?ó?é?¬C. Also because it contains slightly negatively charged oxygen atoms and slightly positively charged hydrogen atoms making it polar. Water has been called a universal solvent because of it polarity. This means it can easily ionise substances, Many compounds, whether ionic, polar or covalent will dissolve...
filters out harmful ultra-violet rays from the sun.

Water"s unique role is due to its physical and chemical properties, they allow water to act as an excellent solvent because of its polarity, water is an excellent support mechanism because of its cohesive forces within molecules and being virtually incompressible, this also means water is a good protective fluid. Water is also important because of its abundance. Although, as all life evolved in water, but some organisms having moved onto land, they will all still rely on the conditions they found and used to their advantages in their original habitat