Abstract: The paper presents an underwater source radiating biharmonic wave of finite amplitude. The source is designed as an array of many elements. Results of experimental investigations allow to assess the pressure field distribution of examining source. Special attention was paid to the observation of phenomena in the area of forming nonlinear waves. Two transmitting arrays were used, both consisting of 16 circular transducers. The resonant frequency of radiating elements equals to 600 kHz or 1.5 MHz, respectively. The frequency range of the first of the sources is 540 kHz - 660 kHz and of the second 1.2 MHz - 1.8 MHz. lnvestigation was carried out for various pressure values at the radiating surface.