The ANTARES detector, located 40 km off the French coast, is the largest deep-sea neutrino telescope in the Northern Hemisphere with an instrumented volume of more than 0.01 cubic kilometers. It has been taking data continuously since 2007. The KM3NeT-ARCA telescope is currently under construction in the Mediterranean sea and has been designed to be the next generation deep-sea telescope with an instrumented volume of the order of the cubic kilometer. Both telescopes consist of an array of optical modules detecting the Cherenkov light induced by charged leptons produced by neutrino interactions in and around the detector. The first detection lines of KM3NeT have been deployed successfully and the first muons observed. Their primary goal is to search for high energy astrophysical neutrinos as diffuse flux or coming from astrophysical sources such as Active Galactic Nuclei or Galactic sources. The search program also includes multi-messenger analyses based on time and/or space coincidences with other cosmic probes.