Electrohydraulic pulsed discharge has been widely adopted in the industrial field over the decades. The proper description of the plasma channel and the induced shock wave contributes to the development of the technology. Experiments were carried out under different voltages and conductivities. The optical pictures were captured using a high-speed camera. The radii of the plasma channel were calculated using cylindrical approximation and spherical approximation, respectively. The results of the calculation have been verified by comparing the measured and calculated radii. The shock wave intensity can be properly calculated using the piston model in the accelerated expansion phase. It provides a better understanding of energy efficiency under different breakdown voltages. In addition, the oscillation of the cavity under different water conductivities was also recorded and compared. The water conductivity has an obvious effect on the maximum volume by changing energy consumption.