The underwater neutrino telescope ANTARES, running in its final configuration since 2008, and the next-generation experiment KM3NeT, with its high-energy component KM3NeT/ARCA, currently being deployed in the Mediterranean Sea, share a common aim: the search for high-energy neutrinos of astrophysical origin. ANTARES instruments a volume of approximately 0.01 km3. Thanks to its excellent visibility of the Galactic Centre and a very good angular resolution, the experiment has already set valuable constraints on the origin of the cosmic neutrino flux discovered by the IceCube Collaboration. Among other efforts, ANTARES is involved in a rich multi-messenger program which includes searching for neutrinos in coincidence with promising transient astrophysical events, as well as triggering electromagnetic follow-up of interesting neutrino candidates by sending alert messages to the Astronomical community. Moreover, the experiment has provided strong constraints on the dark matter cross section by looking for dark matter signatures in massive objects like the Sun and the Galactic Centre. The ANTARES telescope has proved to be a highly successful instrument, performing a wide range of physics analyses. The competitiveness of the results achieved demonstrates the huge potential of the new, cubic kilometre-sized array, KM3NeT/ARCA. The main results achieved by ANTARES together with the status and prospects of KM3NeT/ARCA will be summarised in this talk.