A wave energy converter , comprising a buoyant body , an acceleration tube suspended from and attached to the buoyant body and having an upper end adjacent to the buoyant body and a lower end at a distance from the buoyant body, wherein a portion of the acceleration tube defines a working cylinder between the upper end and the lower end, upper and lower openings in the acceleration tube for allowing a substantially unimpeded flow of water between the working cylinder and a body of water in which the acceleration tube is at least partially submerged when the wave energy converter operates as a result of wave movements, a working piston reciprocable in the working cylinder , an energy conversion assembly comprising at least one energy collecting device collecting energy from the movements of the working piston relative to the buoyant body resulting from said wave movements, and a mooring system adapted to maintain the wave energy converter within a desired anchoring area and comprising at least a first fastening device mounted on the buoyant body for attachment of a first mooring line to the buoyant body and at least a second fastening device mounted on the buoyant body 101 for attachment of a second mooring line to the buoyant body , wherein the first mooring line consists of a first line section for attachment to the first fastening device and of a second line section for attachment to a first anchor placed or intended to be placed at a first anchor position (PI) located outside a first side (SI) of the desired anchoring area , wherein the second mooring line consists of a first line section for attachment to the second fastening device and of a second line section for attachment to a second anchor placed or intended to be placed at a second anchor position (P2) located outside a second side (S2) of the desired anchoring area , wherein at least one of the mooring lines (111; 111') comprises at least one buoyant element (115; 115') attached between the first line section (112; 112') and the second line section (113; 113')) so as to, after positioning of said anchors (114; 114'), attachment of said second line sections (113; 113') to said anchors (114; 114'), pre-tensioning of each mooring line (111; 111') provided with a buoyant element and attachment of said first line sections (112; 112') to the buoyant body , allow that each mooring line (111; 111') provided with a buoyant element, as a result of inherent buoyancy of said buoyant element (115; 115'), will exhibit an angle (a, a') dependent on said pre-tensioning between said first line section (112; 112') and said second line section (113; 113'), which enables each mooring line (111; 111') provided with a buoyant element to be kept taut by means of the buoyant element, when the wave energy converter operates as a result of said wave movements, and that the lengths of the first (112; 112') and second (113; 113') line section, respectively, and the buoyancy of the buoyant element (115; 115') of each mooring line (111; 111'), and the pre-tensioning of the respective mooring lines (111; 111') are adapted to ensure that each buoyant element (115; 115') is located under the water surface at mean water level. <EOS>