Offshore platforms and ocean structures endure wave impact loads due to transient steep waves, including wave breaking events during their design life. The present study aims to understand the nature of the impact pressure and vertical wave-in-deck impact force on a horizontal deck under the action of the regular and breaking waves through experimental investigations. The model details, wave simulation, vertical wave-in-deck load, and pressure variation along the wave direction on a thin plate are presented in the present paper. The maximum breaking wave impact pressure on the plate increases with the air gap up to about one-eighth of the maximum wave height and further decreases with an increase in the air gap.