A power take-off apparatus for a wave energy converter of point absorber type, comprising: - a cylinder adapted to be attached to a floating device and comprising a first upper end and a second lower end; - a piston arranged reciprocating inside the cylinder and having a piston rod adapted to be attached to a mooring; - at least one penstock arranged parallel to the cylinder and comprising a first lower end in fluid communication with the second end of the cylinder through a first opening therebetween, and a second upper end comprising a second opening; - a housing arranged above the first end of the cylinder, wherein the housing is in fluid communication with the penstock through the second opening; and - a water turbine arranged inside the housing and oriented such that working fluid entering the housing from the at least one penstock through the second opening causes rotation of the water turbine to drive an electrical generator connected thereto; wherein working fluid present in the second end of the cylinder below the piston will enter into the at least one penstock through the first opening and exit the at least one penstock through the second opening in response to a downward stroke of the piston in relation to the cylinder; wherein the housing is in fluid communication with the first end of the cylinder through a third opening in a bottom of the housing such that the cylinder, the at least one penstock and the housing together form a closed loop for a working fluid in the power take-off apparatus; and wherein the power take-off apparatus further comprises at least one forward conduit having at least one one-way valve arranged to allow passage of the working fluid only in a direction from the first end of the cylinder above the piston through the at least one forward conduit to the second end of the cylinder below the piston in response to an upward stroke of the piston in relation to the cylinder. - a cylinder adapted to be attached to a floating device and comprising a first upper end and a second lower end; - a piston arranged reciprocating inside the cylinder and having a piston rod adapted to be attached to a mooring; - at least one penstock arranged parallel to the cylinder and comprising a first lower end in fluid communication with the second end of the cylinder through a first opening therebetween, and a second upper end comprising a second opening; - a housing arranged above the first end of the cylinder, wherein the housing is in fluid communication with the penstock through the second opening; and - a water turbine arranged inside the housing and oriented such that working fluid entering the housing from the at least one penstock through the second opening causes rotation of the water turbine to drive an electrical generator connected thereto; wherein working fluid present in the second end of the cylinder below the piston will enter into the at least one penstock through the first opening and exit the at least one penstock through the second opening in response to a downward stroke of the piston in relation to the cylinder; wherein the housing is in fluid communication with the first end of the cylinder through a third opening in a bottom of the housing such that the cylinder, the at least one penstock and the housing together form a closed loop for a working fluid in the power take-off apparatus; and wherein the power take-off apparatus further comprises at least one forward conduit having at least one one-way valve arranged to allow passage of the working fluid only in a direction from the first end of the cylinder above the piston through the at least one forward conduit to the second end of the cylinder below the piston in response to an upward stroke of the piston in relation to the cylinder.