One of the main questions in Physics is the origin of high-energy cosmic rays. In the last decades great progress has been made related to their energy spectrum and composition but their origin remains uncertain. The observation of cosmic neutrinos can enlarge the information, as they can emerge from dense media and travel across cosmological distances without being deflected by magnetic fields nor absorbed by ambient matter and radiation. ANTARES is the first undersea neutrino telescope and the only one currently operating. Its location in the Northern Hemisphere allows for surveying a large part of the Galactic Plane, including the Galactic Centre, thus complementing the sky coverage of the IceCube detector installed at the South Pole. ...