Underwater single gap spark discharge generates shock waves, but it has limitations in increasing its effective area through the control of electrical parameters. To address this, increasing the number of gaps has been proposed as a method to extend the range of shock waves. This study aims to understand the characteristics of multi-gap spark discharge and the generation of shock waves depending on gap conditions through experimental observations. The experiments were conducted to observe changes in shock wave generation characteristics, with a specific focus on shock wave intensity resulting from electrical conditions and gap spacing in double-gap discharge. By measuring the shock waves generated in a double-gap, it was observed that the intensity of the shock wave produced in the longer gap was generally greater. Furthermore, as the gap spacing increased, the difference in shock wave intensity generated at each gap also increased. Based on the observation of shock wave generation from gap discharge, it can be inferred that increasing the gap spacing leads to a stronger shock wave due to the elongation of the discharge path. One of topics of future research would be to find the optimal conditions for the gaps that allow for the synchronization of shock wave generation while ensuring uniform intensity of the two shock waves.