The objective of the project is to study, develop, and test advanced systems for the coordinated operation of two underwater vehicles: the PHOENIX AUV (US Naval Postgraduate School, Monterey, CA, USA) and the INFANTE AUV (Instituto Superior Tecnico, Portugal). The envisioned missions aim at determining the spatial extension of hydrothermal vent fields in the Azores, at close range. This project builds heavily on the results obtained in the project ASIMOV. Its main thrust is the coordinated operation of two AUVs: i) the INFANTE AUV will carry a broad search in an area to detect the occurrence of hydrothermal activity, and ii) the PHOENIX AUV will receive (via the INFANTE AUV) the coordinates of the regions where the hydrothermal activity is judged relevant after which it will approach and conduct hovering maneuvers over selected hydrothermal vents for close range inspection. This is possible in view of the smaller size of the PHOENIX AUV.