Fourth edition of the Rapid Environmental Assessment (REP13) exercise () organized in cooperation with the Portuguese Navy, Portugal, 2013. The exercise took place off the coast of Sesimbra, Portugal, but continued further south from the Portimão airfield. It involved participants from MBARI (USA), Evologics (DE), and the Norwegian University of Science and Technology (NOR). Several large and small propeller-driven ASVs, AUVs with different sensors and acoustic modems were deployed from Bacamarte, a ship from the Portuguese Navy. Several PITVANT UAS were used in these experiments, some being deployed and recovered from civilian airports under monitoring of the Portuguese Air Force, and others launched and recovered aboard Bacamarte. The exercise was targeted at applications in Mine Warfare, Harbour Protection, Expeditionary Hidrography, Search and Rescue, Maritime Law Enforcement, and Rapid Environmental Assessment.