Abstract: Water is treated with sound waves produced by means of a submerged plasma sparking device (16) to mitigate detrimental effects of aquatic organisms in the water. For example, the incrustation of zebra mussels may be reduced by killing the zebra mussels or creating an environment hostile to them. The plasma sparking device may have a main storage circuit (14) which includes liquid dielectric capacitors or cryogenically cooled field coils for storage. Moreover, the electrodes (50) of the plasma sparking device may be of aluminum or an aluminum alloy.