<p>On the basis of the model tests, this paper explores the coupled hydrodynamic performance of the moonpool and the hull. This study aims to compare and analyze the variation in the hull heave response between the piston resonance state of the moonpool under wave excitation and the non-resonance state of the moonpool under wave-current excitation. A novel damping device specifically designed and fabricated for stepped moonpools has been developed. Before and after the installation of the damping device, the free surface response characteristics of the moonpool and heave motion response characteristics of the hull are compared. The findings show a clear correlation between the current speed and heave response characteristics of the hull. During the seakeeping design phase of the drilling vessel, the current speed is an additional critical factor that cannot be disregarded, alongside the moonpool effect. A correlation exists between the fluid dynamics occurring within the moonpool and the heave motion of the vessel hull. A reduction in the amplitude of the motion of the moonpool water results in a decrease in the heave motion of the hull. This study provides a reference for alleviating the seakeeping of a drill ship’s heave response and enhancing the safety and efficiency of the operation.</p>