Flow around fish habitat structures (e.g., boulder, rock) is of great interest, particularly for ?sh passage technology. Modelling such three-dimensional (3D) complex hydraulics associated with a habitat structure using an industrial 2D code solving Saint Venant equations may appear at ?rst as a challenge. The purpose of this study is to determine the ability of a 2D code (River2D) to model ?ow through rock-ramp type nature-like fishpass and its limitations. The model was tested based upon the comparison between numerous experimental measurements and numerical simulations. The impact of varying computational mesh discretization on the accuracy of simulating velocities and water-surface elevations was investigated using the River2D model. The results demonstrate that 2D shallow water modelling using an industrial code River2D can be a convenient way for the hydraulic engineer to help design a nature-like ?shpass. Finally, the performance of rock-ramp ?shpass is discussed in the context of ?sh resting zones, volumetric dissipated power, fish kinematics/energetics, and ?sh swimming performance.