An acoustic source for seismic exploration has a generally cylindrical tubeith spaced upper and lower closed ends. An insulated continuous conductor has a first portion with an exposed internal conductive end within the tube and a second portion extending therefrom through the upper end. A selectively closeable port is operably associated with the tube for permitting the tube to be filled and maintained filled with a conductive solution. A gas vent has a first open end within the tube adjacent the upper end and a second end exteriorly disposed of the tube.