A water molecule is held together by polar covalent bonds. Because the electrons

High surface tension results from attractive forces between water molecules. Smaller organisms can travel across the surface of the water if they don't break these weak bonds. Water has a lower density when frozen, which means that it will float, insulating aqueous habitats. Its high boiling point/heat of vaporization means that animals can utilize it for cooling. Heat/energy from the animal is transferred to the water, which then evaporates. Water is also an excellent solvent for charged molecules such as Na+, K+, and Cl-. The concentration of these solutes can then be used by the organism to generate electrochemical gradients. They may also be used to alter the freezing point or osmotic pressure of an organism's internal environment.