The invention relates to a rudder for sea vessels, consisting of a main rudder and a fin which is coupled thereto by means of a vertical piston (15), restrictively guided by the main rudder and provided with a horizontal piston (11) The vertical piston (15) and the horizontal piston (11) are connected to each other via a hinge bolt to form a sliding pivoting piston coupling (100) and a bearing housing (16) of the vertical piston (15) is fixed to the hull of the vessel. In order to reduce the forces acting upon the sliding bearing of the vertical coupling bolt and horizontal pivoting bolt in addition to the hinge bolts connecting said bolts, the vertical piston (15) is supported by an additional counter bearing (27) on the hull of the vessel.