A theory of electromagnetic surface wave propagation on a plane superconductor-vacuum interface is presented for a superconductor with strong coupling. The solution of a self-consistent equation for the energy of elementary excitations is obtained in terms of modified u-v transformation method. The linear response (conductivity) tensor is analysed in the framework of a non-local description allowing for the finite dimension of the Cooper pair. Within the framework of the semi-classical infinite-barrier model the surface wave dispersion relations are calculated analytically and numerically for the cases of strong-, intermediate-, and weak-coupling superconductors.