Ultrasonic waves incident at the interface between two linear media will be reflected based on the linear reflection coefficient, which depends on the linear acoustic impedances of the media. However, propagation of ultrasonic waves in quadratically nonlinear media can lead to nonlinear reflection coefficients which are dependent on the frequency, source amplitude, and nonlinearity of the two mediums. The objective of this work is to explore the existence of a nonlinear reflection coefficient between two mediums using analytical, numerical, and experimental methods. For simplicity and consistency, a water-solid interface was chosen and finite amplitude ultrasonic waves between 2.25 MHz and 25 MHz were used to study the interfacial response. The analytical results show the existence of a nonlinear RC, but whose effect is very minimal. Experimental and numerical results show that the transfer of energy in harmonic generation affects the RC more than other factors. The influence of several factors like interaction zone, shock generation, etc. will be discussed.