A seismic wave generating tool, such as a spark gap, of an electric arc generation device includes an upper part and a lower part defining a discharge chamber between them, at least one retaining arm connecting the upper part to the lower part, first and second electrodes respectively associated with the upper and lower parts and arranged in the discharge chamber. The retaining arm comprises an electrically insulating part facing the electrodes. The tool includes a first deployable device implementing a current return and connecting the upper part to the lower part. The first deployable device is configured to be in a retracted state and in a deployed state in which it is at a distance from the discharge chamber.