An acoustic impulse generator is disclosed for use in a fluid media for oceanographic, seismographic and related applications. The generator includes a housing with a piston slidably disposed therein and a passageway through which a rod attached to the piston moves. A firing chamber is attached to the housing for channeling a quantity of liquid through a nozzle. A diaphragm may be disposed between the housing and the firing chamber with the quantity of liquid being displaced in response to movement of the piston.