This article discusses the possibility of building online a mosaic of the seafloor relying on a SLAM framework. The goal is to provide the ROV operator with an approximated seafloor's visual map relatively rough. In order to have that map, it is important to get an accurate estimate of the location of the visual landmarks and, in particular, a correct data association when a visual landmark is re-visited by the vehicle. The proposed approach uses the combination of a set of local mosaics constructed in the proximity of the SLAM visual landmarks instead of using a global mosaic. The algorithm was tested using a batch of experimental data in typical operating conditions and the results show the effectiveness of the approach.