An equation for calculating relation of the incident angle and the scattering intensity from a large scale air bubble in water is derived based on the principle of geometrical optics. By neglecting the attenuation factor G, the formula is much simpler than the Davis model. One application of the model is to calculate the angular distribution of the scattering light by a single air bubble. The volume scattering function is simulated with the collimated light incident on the air bubble. It is found that the forward scattering is far greater than the backward scattering. As long as the bubble radius is much larger than the wavelength of light, the angular distribution of the scattering light is not influenced by the change of bubble radius. However, the increase of relative refraction index weakens the forward scattering while strengthens the backward scattering on the bubble surface.