Hydrodynamic characteristics like lift and drag coefficients of a cascade of blades as well as comprehensive data of pressure loss and flow deflection are important for the design of a hydroturbomachine. In the present paper numerical investigation of flow over a cascade of S-shaped hydrofoils is presented. These S-shaped hydrofoils find potential application in the design of a fully reversible pump-turbine employed in tidal power generation. Influences of stagger angle, blade spacing and angle of incidence on the performance of S-blade cascade were investigated and these are reported here. Numerical results are validated with experimental data available in the literature and further simulations help to extend the knowledge of the flow field for such a complicated geometry. It is found from numerical simulations that the useful range of operation is restricted to +6 degrees for turbine operation and -6 degrees for pumping. A significant finding in this study is that the cascade pressure loss is significantly more for the pump cascade than the turbine cascade and this loss increases as the blade spacing is reduced. (C) 2014 Elsevier Ltd. All rights reserved.