Localization and navigation represent a crucial point of the control system of marine robots because of the impossibility of exploiting sensors based on radio waves commonly used for air or land applications (e.g. Global Positioning System - GPS). Sensors based on acoustics are, instead, used to enhance the localization and navigation performance obtainable through Inertial Measurement Units (IMUs) and Doppler Velocity Logs (DVLs). A lot of research activity has been oriented within the scientific community on different integration strategies of the acoustic sensors information with IMU and/or DVL. Within the Interuniversity Center of Integrated Systems for the Marine Environment (ISME), the University of Pisa and the University of Florence nodes began to collaborate on this research topic since several years. In particular, the research is oriented to provide a team of cooperating Autonomous Underwater Vehicles (AUVs) with strong georeferencing capabilities; to this aim, the AUVs are equipped with acoustic modems with both communication and mutual localization capabilities.