The DORIS project intends to develop a modular autonomous surface vehicle (ASV), having the capability to sample the surface micro-layer, and consequently, perform analysis of surfactant films and the biological communities residing within the micro-layer. This proposal integrates strong technological and scientific components, from conception to validation of the sampling and navigation systems. The scientific and engineering synergy of this project provides opportunities to use the vehicle in two specific study cases: a coastal study (Douro River plume) and an estuarine study (Ria de Aveiro). With these we will validate the methods and observational requirements previously defined by the scientific and engineering partnership. The long term overall objective will be therefore to contribute to a better knowledge of surfactant films formed in the interface of riverine and coastal waters, as well as to enhance our knowledge of bacteria and viruses biodiversity in the Ria Aveiro.