1) Water is a very weak nucleophile due to the lone pairs that are present on the oxygen.
2) hydroxide is the conjugate base of water (OH-). Water in its natural state is fairly comfortable and isn't too keen about making an extra bond with anything else (i.e. reacting to it).
But OH- is incredibly reactive because it needs to use its negative charge to make a bond with something (i.e react with it).
3)Water is a polar molecule. The reason for this is the electronegativity within the molecule itself, Oxygen has a much higher electronegativity than Hydrogen. The natural bent shape of oxygen results in a dipole moment towards the oxygen from both of the hydrogens, this gives the molecule a net negative dipole towards the oxygen and a net positive dipole towards the hydrogens, allowing it to be the perfect polar solvent.