Under the joint chairmanship of the prefects of Reunion, Mayotte and the French Southern and Antarctic Territories (TAAF), the ultramarine maritime council of the South Indian Ocean Basin (CMUB) met in plenary session on Wednesday 22 November 2017 in Saint-Denis. This third session of the CMUB was an opportunity to take stock of the work done for the preparation of the South Indian Ocean Sea Basin Strategic Document (DSBM) and to discuss the functioning of the Council since the last plenary session of December 14, 2016. An initial version of the inventory of the South Indian Ocean Basin, the fruit of the work of the 4 working groups (environmental protection, risk prevention and coastline management, knowledge, research, innovation and education-training, maritime and coastal activities) was thus presented. This document is intended once finalized to constitute, in addition to the issues identified by the working groups, the diagnosis or zero state of the basin, prior to the adoption of the action plan that should take place within a year. The roadmap for the actions to be taken in 2018 has been validated: it notably provides for synergies with concomitant projects, particularly with regard to maritime spatial planning. (…)