Objectives  The hydrodynamic performance under different bailer conditions based on numerical and experimental methods was investigated.

  Methods  The hydrodynamic performance of the seaplane with different displacements under different speeds was studied using an experimental method, and the viscous flow field of the seaplane under three conditions（without bailer, bailer closed, bailer lowered) at different speeds was computed.

  Results  The results show that at the same displacement the total resistance and heave amplitude of the seaplane increase, the trim angle decreases, when the speed increases; with displacement increases, the total resistance, trim angle and heave amplitude of the seaplane increase; while the bailer lowers, the total resistance and heave amplitude of the seaplane increase, the trim angle decreases; the effect on the hydrodynamic performance is not obvious as the bailer closes.

  Conclusions  The results of this paper are of great significance to the optimal design of water pumping systems of the seaplane.