Abstract: If the frequency of the incident sound wave coincides with one of the eigenfre-quencies of the underwater elastic cylinder, the corresponding eigenvibration will appear excited by the incident sound wave and then strongly reradiate sound wave towards surrounding water. It has been revealed by previous investigations that the amplitude of backscattering sound appears to be minimum at the eigenfrequencies of the underwater metallic cylinders because of the destructive interference between reradiated wave of the eigen vibration and the geometrical reflected wave from surface of the cylinders. In this paper, a new p enomenon has been revealed. The amplitude of back scattering sound appears to be maximum at t e eigenfrequencies of a cylinder made from non-metallic material in which the velocity of elastic transverse wave is less than the sound velocity in water.