NOVELTY - The arrangement in wave energy recovery system has a wing element that is hinged on its one edge to make a reciprocating motion in response to kinetic energy of waves or tidal currents. A wave energy recovery unit has a space (6a) which alters its volume with the help of a connection rod (3) making a reciprocating movement caused by the wing element. The sealings and/or through holes provided between the space and the connection rod are protected against seawater. A hydraulic cylinder (6) has a piston (3b) that is fastened to move with connection rod.    USE - Arrangement such as protective arrangement in wave energy recovery system.    ADVANTAGE - The reliable and efficient arrangement in a wave energy recovery system can be achieved. The provided arrangement can capture a maximum amount of available wave or tidal energy and convert it efficiently to electric energy or to another suitable energy without a need to be serviced too often due to a failure caused by a hostile seawater neighborhood. The environmentally friendly arrangement is formed in wave energy recovery system, which does not leak for instance hydraulic oil through worn out or damaged bushings to seawater. The hydraulic cylinders and piston rods with their bushings and sealings are protected against seawater, so that the lifetime of the hydraulic cylinders and their components can be increased at longer maintenance intervals and lower operation costs. The cost savings can be achieved in materials because changing intervals become longer. The reliability of the installation becomes better and the continuous energy production can be achieved without disturbing interruptions. Hence the productivity and competitiveness can be improved and improved friendliness is provided to the environment.    DESCRIPTION OF DRAWING(S) - The drawing shows the cross section illustrating the simplified and diagrammatic representation of protective arrangement of the wave energy recovery system.    Connection unit (3)    Sleeve ring (3a)    Piston (3b)    Hydraulic cylinder (6)    Space (6a)