"The observation of high-energy cosmic neutrinos, produced in distant astrophysical accelerators (and possibly by means of more exotic processes as well), has turned into one of the major challenges of today’s astroparticle physics, motivated by the possibility to open a new observational window on the distant Universe. The present project is a contribution to the experimental effort being carried by the european scientific community to build a large-scale undersea neutrino telescope in the Mediterranean. The efficiency of the data collection and analysis will be assessed through the study of the performance of the prototype instrument ANTARES (currently being deployed offshore near Toulon, France), in order to optimize the detection potential of the telescope, with a particular attention to neutrino point sources searches. The sensitivity of the telescope to ultraenergetic neutrinos, as well as to possible signatures of new physics, will also be investigated. A technical contribution will be dedicated to the characterization of the optical modules ageing in conditions of irradiation (e.g. bursts of bioluminescence) similar to those encountered in the deep sea. The interpretation of the first data on the basis of up-to-date astrophysical and cosmological models will provide important benchmarks for the subsequent building of a cubic-kilometer-sized detector in the Mediterranean, now in design study in the KM3Net collaboration."