<p>In the maritime industry, composite materials have increasingly replaced traditional metals and alloys in components, such as propellers, hulls, bulkheads, hatches, and superstructures, due to their superior mechanical and chemical properties. These composites offer advantages like higher specific strength, lighter weight, reduced acoustic emissions, delayed cavitation onset, and better resistance to thermal and chemical effects. By adjusting the reinforcement, matrix material, and stacking sequence, the strength and stiffness of composite materials can be tailored for various applications. This paper aims to study the hydro-structural performance of composite marine propellers under uniform flow conditions. A transient fluid–structure coupling algorithm was developed, combining computational fluid dynamics (CFD) with the finite element method (FEM). Experimental tests were conducted to validate the numerical model. A comparative analysis was performed to assess the differences in open-water performance, pressure distribution, and structural deformation, providing insights into the hydroelastic behaviour and bend–twist coupling effects of glass fibre-reinforced polymer (GFRP), carbon fibre-reinforced polymer (CFRP), and aluminium. The results, specifically for bidirectional fibre orientations, showed a reduction in torque by 7% for CFRP propellers and 10.14% for GFRP propellers compared to aluminium. Additionally, efficiency improved by 6.04% for CFRP and 12.23% for GFRP relative to aluminium propellers.</p>