The present study investigates experimentally and numerically the impact of composite materials on hydro-elastic performances of a hydrofoil experiencing Fluid–Structure Interactions, and focus on the bend–twist coupling phenomenon. Four flexible hydrofoils piercing the free surface, with identical geometry of extruded plan-form, a constant NACA0015 section, are tested in a cantilevered configuration in a hydrodynamic flume. The hydrofoils are built from the same mold with different materials (carbon or glass fiber) and different layups. The layups are designed to allow or not bend–twist coupling by the use of 45°plies in the structure. Two different coupled FSI numerical approaches are developed to model the hydrofoils behavior: a low fidelity code based on the coupling of a Vortex Lattice Method and a beam theory and a high fidelity code made of the coupling of the structural model code–ASTER and an OpenFOAM VoF hydrodynamic model with free surface. Mechanical characterization of the hydrofoils highlights the differences on the structures which are exacerbated in the hydrodynamic tests. The bend–twist coupling induces a modification of the angle of attack at the tip, leading to a significant difference of the generated lift and thus the deformation. The bend–twist coupling and the hydrodynamic performances are simulated by the numerical approaches.