Water makes 70% of the Earth's surface and it makes up as much as 95% of the living organisms.
Water is a polar molecule composed of oxygen and hydrogen. They are attracted by a covalent bond or the sharing of electrons. The oxygen atom attracts the shared electrons much more than the hydrogen atoms. As a result, the oxygen atom acquires a partial negative charge, while the hydrogen atoms acquire a partial positive charge.
Because the oxygen nucleus has strong attraction for the hydrogen electrons, the hydrogen atom is distorted from the usual position resulting in the formation of a 105° angle between the hydrogen atoms.
Because this asymmetry of the hydrogen atoms, the water molecule is highly polarized with a strong separation of positive charge (hydrogen) and negative charge (oxygen). This polarization causes the water molecules to attract to each other.