According to valence bond theory, water molecule has

According to the VBT ,the covalent bond is formed by the overlapping of pure atomic orbitals having unpaired electrons of valency shell of the atoms.

₈O : 1s² 2s² 2p_x²   2p_y²  2p_z¹
In H₂O,the "O" atom in its valency shell contains 2-unpaired electrons in two p-orbitals, those two p-orbitals are perpendicular to each other [i.e., 90° to each other], those two p-orbitals forms the two covalent bonds with two half filled s-orbitals of  hydrogen atoms with an angle of 90°.