The BATHYMAY survey on the VIGO voyage (MD 136/VIGO cruise) was designed for bathymetric mapping of the insular margin outside of the lagoon of Mayotte, using a multibeam echosounder. The geomorphological and structural analysis of the bathymetry is an extension of studies carried out on land to assess natural hazards and specify the morphology of potential areas of fisheries resources. In the framework of its Public Service activities, and partnership with the Collectivité Départementale (@county authority) of Mayotte, the BRGM is conducting a multiannual study of natural hazards taking various unknown factors into account: ground movements, flooding, seismicity, soil erosion and cyclonic surges. Preliminary studies had indicated on the basis of existing data (SHOM 1974 to 2000), the possible existence of volcanic cones, of underwater landslides extending for several kilometers, and of geological faults whose still clear traces suggested that they may be recent. The multibeam bathymetry morphology analysis should make it possible to: -follow the geological (volcanic complexes, faults, etc.) and geomorphological structures (dips, troughs or trenches, etc.) identified on land; survey the marine structures in order to document the old and more recent geological history of the island; -look for geological structures which could be a natural hazard for the island of Mayotte; The Directorate of Agriculture and Forestry of Mayotte, BRGM's partner in this operation, wanted to have accurate surveys in order to develop deep sea fisheries. This falls under the BRGM Public Service - MAYOTTE Bathymetry project.