For streamer acquisition, the reflection of the up-going wave field at the sea surface (or ghost) contaminates the recordings, and in particular, significantly attenuates the lower frequencies. In order to eliminate the ghost, we may choose to advocate the recording of the wave field at two different depths: the so-called 'Over-Under' technique. In this paper, we propose different strategies to combine these hydrophones recordings, taking into account the characteristic of the swell noise which is sometimes a severe issue. We also show that the relative positioning of the cables is not a strict constraint with a proper 3D algorithm. The different algorithms are demonstrated on synthetic and real datasets.