The main goal of this project is to predict the in uence of non-uniform basin depths on the stability of single inlet systems. This is achieved by making use of Escoffier's principle, which poses a relationship between the relative water flow velocity in an inlet and the rate of change of its cross-sectional area. To this end, a thorough analysis is performed on the equations that govern water motions, principially the linearised shallow water equations. An analytic solution is obtained, and some results are simulated in MATLAB.