Free-surface multiples in OBS acquisition are often treated as noise. However, because they are formed by the same source signal as primaries but travel along different paths in the medium, they contain information not presence in the primaries. To capitalize on the information provided by both the multiples and the primaries, we have developed a procedure that allows primary and mirror signals to be jointly imaged. While direct migration of the primary has limited illumination aperture, direct migration of the mirror signal is less resolved in complex areas. Joint inversion results in better illumination, improved resolution, and a more balanced amplitude image in geologically complex models.