In recent years, microorganisms contained in ship ballast water have been identified as vectors for the destruction of marine ecosystems. To control such microorganisms, various techniques are being developed and tested. As part of this effort, we propose a technique that uses underwater shock waves driven by a gas-imploding detonation. Previously, we have reported characteristics of pressure generation at the implosion center of an imploding detonation. We examined how the maximum pressure, rise time, and half-width time of underwater shock waves affected the mortality rate of microorganisms (Anemia salina). The mortality rate of Artemia salina was increased by shortening the rise time of the pressure waves while increasing the maximum pressure and half-width time of underwater shock waves.