Waves, a constant presence in the ocean, significantly influence the stability of a vehicle's water entry. In the present work, the effects of waves on the water entry of a vehicle equipped with a cavitator, utilizing the Computational Fluid Dynamics (CFD) method. The Stokes V wave theory serves as the basis for wave simulations, while the moving computational domain method is used to realize the motion of the vehicle. The water entry process is most influenced by waves at the peak point of wave inclination. This research delves into the impacts and underlying mechanisms of wave height, entry angle, and speed on the water-entry process, particularly focusing on the range of wave influence. Re-entry may occur when the entry angle is smaller than the maximum wave inclination. Under such circumstances, the vehicle's motion could become more erratic, potentially leading to re-entry failure. Consequently, two critical angles are defined: one where re-entry is likely to occur, and another where re-entry is inevitable. The influences of wave parameters and entry angle on the possibility of re-entry are investigated. The proposed critical angles and their calculation method lay the groundwork for future research aimed at ensuring safe water entry for vehicles amid waves. •The fluid-structure coupling between waves and vehicles is realized using moving computational domain method.•Two critical angles are defined as the water-entry angles where re-entry is likely to occur and bound to occur.•A theoretical method for calculating the probability of re-entry is established.•The law of influence of the entry and wave parameters on the range of wave influence on the water entry is obtained.