Nowadays, Autonomous Underwater Vehicles (AUVs) become significant contributors to Rapid Environment Assessment (REA). Indeed, a variety of acoustic sensors can be mounted on AUVs allowing a complete seafloor representation (images, 3d data, video, sub-bottom layers, etc.). The AUV DAURADE platform is a new generation of AUVs. It can acquire bathymetry simultaneously with two acoustic sensors: a multibeam echo sounder (MBES) and an interferometric sidescan sonar (ISSS). In this paper, we propose a framework to fuse the bathymetric data coming from the two swath bathymetric sensors using the theory of belief functions. Here in after, obtained results on actual data are discussed.