This paper is an examination of semi-empirical techniques which are shown to be effective in predicting the response of hydrofoils to flow excitation. Examples are given for buffeting by inflow turbulence, excitation by the boundary-layer pressures on the hydrofoil, and linear and non-linear excitation by vortex street formation in the wake. Co-ordinated aerodynamic and hydrodynamic measurements are used in Reynolds number - scaled experiments to determine both the flow induced forces and the hydro-elastic behavior on cantilever struts. An analytical formulation based on normal mode theory is used to combine the results
