Nonlinearity in the piezoelectric response limits the operating conditions of underwater transducers. In this work, the nonlinear effects are evaluated in terms of electrical current and induced strain as a function of drive level. Nonlinearity is further quantified within the active transduction material by evaluating the total harmonic distortion (THD) in the electromechanical response. Modified single crystals based on the binary lead magnesium niobate—lead titanate system were investigated. It is shown that single crystals show greater mechanical response and reduced THD, enabling operation at higher power levels. The performance of these single crystals is also compared to conventional high power lead zirconate titanate ceramics.