This paper analyses the stability of rigid waterfront structures, as caisson quay walls, by using the traditional pseudo-static method. The current procedures to calculate the forces acting on such structures under seismic condition are discussed. The case of partially submerged backfill is particularly focused and a new approach is proposed. Referring to stability against a sliding mode of failure of a typical waterfront wall, a comparison among different methods of analysis is presented and the effects of water to wall height ratio, excess pore water pressure and horizontal seismic coefficient are also highlighted.