NOVELTY - The arrangement has an adjustment unit for adjusting a total effective surface area of a set of plate-like wings (3a) of a wave energy recovery system. A movement control unit (10) controls change of the total effective surface area and/or a vertical position of the wings. A detector unit (11) recognizes prevailing ocean conditions and is connected to a control system of the wave energy recovery system. The detector unit gives information to reduce the surface area of the wings or to lower the wings nearer to a sea bottom in relation to strength of sea conditions.    USE - Arrangement for a surface area adjustment of a reciprocating wing system in a wave energy recovery system for recovering kinetic energy e.g. wave energy and tidal energy, from seawater during calm ocean conditions and stormy ocean conditions to produce electric energy for main electric networks and fresh water. Can also be used for different tidal conditions.    ADVANTAGE - The adjustment unit adjusts the total effective surface area of the plate-like wings of the wave energy recovery system, thus adjusting the total effective surface area of the wings according to prevailing ocean conditions in an easy manner, and hence enabling the wave energy recovery system to capture maximum amount of wave energy during any kind of ocean condition in a reliable and efficient manner. The arrangement captures large amount of energy in calm conditions when the waves are small. The arrangement is protected against stormy sea conditions. The wings are arranged totally under the surface of the water, so that undesirable parts of the wave energy recovery system are not visible.    DETAILED DESCRIPTION - The adjustment unit is designed as a size adjustment unit and a height adjustment unit.    DESCRIPTION OF DRAWING(S) - The drawing shows a front view of a large-sized plate-like wing of a wave energy recovery system.    Recovery unit (3)    Plate-like wings (3a)    Hinges (6)    Movement control unit (10)    Detector unit (11)