Apparatus, computer instructions and method for processing seismic data related to a subsurface of a body of water. The method includes inputting data indicative of recordings made by detectors provided on a depth-changing profile in response to an acoustic wave reflected from the subsurface; applying a matched mirror migration procedure to the data, where (i) actual positions of the detectors on the depth-changing profile and corresponding recordings, and (ii) fictitious mirror positions of the actual detectors on the depth-changing profile and corresponding recordings with a changed sign are added in the matched mirror migration; and generating a final image of the subsurface based on the matched mirror migration procedure.