It is essential for cars to display a level of waterproofness that enables them to drive over a flooded road without stalling or other negative consequences. A project seeking to replace driving tests on flooded roads by simulation has developed a simulation technology using the VOF method. It was demonstrated that appropriately imparting the degree of change in vehicle speed and vehicle height and the engine intake amount during the test as the simulation conditions makes it possible to reproduce the pattern of water infiltration and the amount of water infiltration resulting from differences in the shape and the position of the intake ports. However, while a predictive technology is necessary in the initial stage of vehicle development in order to reduce the necessity for repeating procedures in later stages, because there are no prototypes at the initial stage of development, these degree of change in vehicle speed, intake amount, and vehicle height, which are used as simulation conditions, are unknown. A technology making it possible to predict these parameters in advance was therefore developed in tandem with the simulation technology. The developed technology was applied to models with differing frameworks and engine types, and its effectiveness as a technology for the predictive simulation of waterproof performance at stages of the vehicle development process prior to the production of prototypes was verified.