A wave power device for extracting energy from water waves, the wave power device comprising: - a substantially stationary member - an effector being directly or indirectly connected to the substantially stationary member and being configured for moving relative to the substantially stationary member when wave forces are acting on the effector, wherein - the effector is configured to move parallel to a length axis of the substantially stationary member, from a predetermined center position on the substantially stationary member, in either one of two directions being opposite to each other, the wave power device further comprises at least two hydraulic rams (14a, 14b), preferably being symmetrically arranged around each effector along the length axis of the substantially stationary member, wherein the at least two hydraulic rams (14a, 14b) each comprise: - a base section, at least one pipe section and a center section, wherein the center section is configured for sliding into and out of a pipe section and a pipe section is configured for sliding into and out of the base section, wherein the sections (142, 143, 144) together enclose a sealed space, having a volume which are decreasing or increasing when the sections (142, 143, 144) slide into and out of each other respectively, - an inlet comprising a valve, for inletting water into the enclosed space within the hydraulic ram (14a, 14b), when the length of the hydraulic ram (14a, 14b) is increasing, - an outlet comprising a valve, configured for outletting pressurized water from the enclosed space within the hydraulic ram when the length of the hydraulic ram (14a, 14b) is decreasing, preferably into a pressure pipe, wherein the base section or the center section are fixed at a pre-determined position on the substantially stationary member and the other is directly or indirectly connected to the effector, in a way so when the effector moves relative to the substantially stationary member: - the effective hydraulic area of at least one of the at least two hydraulic rams (14a, 14b) is stepwise increased as the moving effector decreases the length of that hydraulic ram and - the effective hydraulic area of at least one of the at least two hydraulic rams (14a, 14b) is stepwise decreased as the moving effector increases the length of that hydraulic ram. - a substantially stationary member - an effector being directly or indirectly connected to the substantially stationary member and being configured for moving relative to the substantially stationary member when wave forces are acting on the effector, wherein - the effector is configured to move parallel to a length axis of the substantially stationary member, from a predetermined center position on the substantially stationary member, in either one of two directions being opposite to each other, - the effector is configured to move parallel to a length axis of the substantially stationary member, from a predetermined center position on the substantially stationary member, in either one of two directions being opposite to each other, - a base section, at least one pipe section and a center section, wherein the center section is configured for sliding into and out of a pipe section and a pipe section is configured for sliding into and out of the base section, wherein the sections (142, 143, 144) together enclose a sealed space, having a volume which are decreasing or increasing when the sections (142, 143, 144) slide into and out of each other respectively, - an inlet comprising a valve, for inletting water into the enclosed space within the hydraulic ram (14a, 14b), when the length of the hydraulic ram (14a, 14b) is increasing, - an outlet comprising a valve, configured for outletting pressurized water from the enclosed space within the hydraulic ram when the length of the hydraulic ram (14a, 14b) is decreasing, preferably into a pressure pipe, - the effective hydraulic area of at least one of the at least two hydraulic rams (14a, 14b) is stepwise increased as the moving effector decreases the length of that hydraulic ram and - the effective hydraulic area of at least one of the at least two hydraulic rams (14a, 14b) is stepwise decreased as the moving effector increases the length of that hydraulic ram.