From the time we are in diapers until we are ferried across the River Styx, water is so much a part of life that we mostly take it for granted. More than half of each living thing on Earth is water. In addition to being the all-pervading fluid of life, water is the custodian of most of the Earth's available energy. More so than most substances, water is capable of storing much heat energy. As water moves within the global circulation of the atmosphere and the oceans it helps transport solar energy received in the tropics to the polar regions and thereby moderates the environment of the whole planet.
Water is said to be the universal solvent, able to dissolve most other substances.
Also, it is the best wetting agent by virtue of its ability to bond onto and coat the surfaces of many materials, even hard, slick substances such as glass. Water owes its array of strange properties to the unusual way oxygen and hydrogen atoms cling together to form water molecules. The atoms in most molecules are bonded together by only one of two kinds of forces, but a water molecule is held together by both kinds. This causes a tricky balancing act because the two forces each try to establish different spacings between the hydrogen and oxygen atoms. Furthermore, at least one of the forces is temperature-dependent and extends outside the molecule to affect nearby molecules.