The general objective of the EU STREP EXOCET/D (GOCE-CT-2003-505342) was to develop, implement and test specific technologies aimed at exploring, describing and quantifying biodiversity in deep-sea fragmented habitats as well as at identifying links between community structure and environmental dynamics. The first leg of the MoMARETO cruise, held in summer 2006 on the new French oceanographic vessel Pourquoi pas? constituted the final demonstration action of EXOCET/D. In addition to sea trials, the scientific objective of the cruise was to study the spatial and temporal dynamics of hydrothermal communities colonizing active hydrothermal sites on the Mid- Atlantic Ridge. Three vent fields, ranging from 850m to 2300m, were visited by the ROV Victor 6000 during the cruise.