If water were a nonpolar molecule, how would the properties of water be different?

Life needs water and depends on the properties of water and those properties depend on the polarity of water. If water was non-polar, water would not be able to form hydrogen bonds and these bonds give water it's high specific heat (takes long to heat and stays hot longer once it is heated). It would not have surface tension (water could not go up trees, bugs could not stand on water and water would not stick to the sides of things). Ice would not float on liquid water (hydrogen bonds creates the crystal lattice so that ice has the unique property of being less dense than the liquid phase). Water would not be able to form hydrogen bonds since co- valent bonding is involved - loss of polarisation would alter the ability of atoms to stick together and since molecules of water already stick together strongly. 

Hope this helps!! (If not sorry!)