The recently developed Consistent Particle Method (CPM) is improved to eliminate pressure fluctuation such that fluid–structure interaction problems can be accurately simulated with a partitioned coupling procedure. The strategy of smoothing pressure is to combine a zero-density-variation condition and a velocity-divergence-free condition to enforce fluid incompressibility. The proposed algorithm is validated by hydrostatic and free-sloshing examples, which show better pressure results with less spurious fluctuations. Using the improved CPM, water sloshing with a constrained floating baffle (CFB) is successfully simulated. The effect of CFB in sloshing mitigation is investigated. Experimental studies are conducted to partially verify the numerical algorithm.