A device for generating electricity comprising: - an electricity generator having a rotatable generating shaft for generating electricity; - a floating frame designed to at least partly support said electricity generator ; - a first roller portion wound around a respective first winding body and a second roller portion wound around a respective second winding body , the winding bodies being mounted on the floating frame and the roller portions being configured to rotate the respective winding bodies ; wherein each winding body is supported by a respective portion of the shaft and is rotatable about an axis of rotation (X1, X2); wherein said first roller portion has an end connected to a sea bed or to a fixed structure and said second roller portion has an end connected to a counterweight ; wherein said winding bodies are mechanically and/or kinematically connected in such a way that when said floating frame is lifted, with the end of the first roller portion fixed to the sea bed or to the fixed structure, a corresponding lifting of the counterweight follows and a lowering of the floating frame is followed by a corresponding lowering of the counterweight ; wherein said portions of shaft are mechanically connected to said generating shaft for transmitting mechanical power to the generating shaft ; and wherein each of said winding bodies is connected to the respective portion of shaft by at least one free wheel designed to transmit a torque between the winding body and the corresponding portion of shaft in a direction of rotation and a free rotation of the winding body relative to the respective portion of shaft in the other direction, in such a way that when the first winding body transmits a torque to the respective portion of shaft the second winding body , kinematically coupled to the first winding body , is freely rotatable on the respective portion of shaft , and vice versa. - an electricity generator having a rotatable generating shaft for generating electricity; - a floating frame designed to at least partly support said electricity generator ; - a first roller portion wound around a respective first winding body and a second roller portion wound around a respective second winding body , the winding bodies being mounted on the floating frame and the roller portions being configured to rotate the respective winding bodies ; wherein each winding body is supported by a respective portion of the shaft and is rotatable about an axis of rotation (X1, X2); wherein said first roller portion has an end connected to a sea bed or to a fixed structure and said second roller portion has an end connected to a counterweight ; wherein said winding bodies are mechanically and/or kinematically connected in such a way that when said floating frame is lifted, with the end of the first roller portion fixed to the sea bed or to the fixed structure, a corresponding lifting of the counterweight follows and a lowering of the floating frame is followed by a corresponding lowering of the counterweight ; wherein said portions of shaft are mechanically connected to said generating shaft for transmitting mechanical power to the generating shaft ; and wherein each of said winding bodies is connected to the respective portion of shaft by at least one free wheel designed to transmit a torque between the winding body and the corresponding portion of shaft in a direction of rotation and a free rotation of the winding body relative to the respective portion of shaft in the other direction, in such a way that when the first winding body transmits a torque to the respective portion of shaft the second winding body , kinematically coupled to the first winding body , is freely rotatable on the respective portion of shaft , and vice versa. <EOS>