Recently, in acoustics, in addition to piezoelectric, magnetostrictive, electrodynamic, electromagnetic, and other converters, electrokinetic converters have become widespread, using various electrokinetic phenomena to convert electrical energy into acoustic (radiators) or acoustic energy into electrical (receivers), or acoustic energy into acoustic (sound repeaters). This field of acoustics is in the process of formation and active development. Many scientific and technical problems related to electrokinetic converters are still under study and practical solution. And, if with electrokinetic converters in the air the task of their creation and application can be considered practically solved, then in a liquid medium (for example, in water) a scientific and practical solution to the problem has not been achieved. The paper considers the comparative efficiency of electroacoustic conversion of an electrokinetic radiator in two media, obtained by modeling on the COMSOL Multiphysics software package: in water and in air. In the course of research, the possibility of modeling the transformation process within the framework of a viscous incompressible fluid model was substantiated, which significantly reduced the complexity of calculations in the modeling process. During modeling, it was possible to get by with a truncated system of electrohydrodynamic equations a closed system of Navier-Stokes equations for an incompressible fluid, which greatly simplified model calculations. The paper presents simulation results that reveal significant advantages of electrokinetic transformation in water compared with electrokinetic transformation in air. In the described simulation, only the losses associated with friction in the liquid were taken into account. In further model studies, it is planned to take into account the losses of electroosmotic electroacoustic transformation associated with heat dissipation. The ongoing research is necessary and useful for the real creation of promising electrokinetic converters operating in both water and air. Keywords: electrokinetic converters, viscous incompressible fluid.