The authors investigate surface waves excited in cold plasma by an oscillating current, considering cases where the plasma is bounded (plasma layer and plasma cylinder). It is physically clear that one has to take into account the actual geometry of the plasma configuration when the damping length of a surface wave is commensurate with the transverse dimensions of the plasma. The authors study the surface waves when the plasma is surrounded by a metallic sheath of infinite conductivity. The conditions are found for the build-up of three-dimensional surface waves and the corresponding expressions derived for their frequencies and growth rates.