Here is presented a new project, MORPHODUNES, dealing with the sub-marine sand dune morphodynamics. It is funded by Shom (French Navy) to develop a fully-coupled 3D hydro-morphodynamic model able to simulate the dune migration over the continental shelf according to the metocean forcings, sediment characteristics and seabed morphology. The first part of the project is related to the physical modelling of an idealized and realistic field of dunes at laboratory scale. The laboratory measurements of the flow characteristics and bed topography will be used to validate and calibrate the hydro-morphodynamic model for some specific processes (e.g. sur-imposed bedforms and impacts). The second part of the project is devoted to the analysis of field data. These data are recorded by Shom in Iroise/Celtic sea, near the Brest harbour during the project. Sedimentary fluxes, bed morphology and thickness of the mobile zone, sediment response of the hydrodynamic conditions will be determined from this analysis. The third part is dedicated to the set-up, validation, and calibration of the hydro-morphodynamic model for the study site thanks to the in-situ data and their analysis. This work will be based on several diagnoses for hydrodynamics and morphodynamics (e. g. flow characteristics, wavelength and height of dunes, asymmetry index, crest sinuosity). At the end, the model should be as much as possible independent of the site conditions to be used to simulate dune morphodynamics in 3D at another location in the world for the marine safety and navigation.