A device adapted for a down-hole seismic source in a down-hole in the subsoil and containing water, the device being adapted for introduction into the down-hole and immersion in water, includes: a cartridge-holding head, having a cavity having a number of firing mouths on the side surface of the head, inclined relative to the longitudinal axis of the head towards the operationally lower end of the closed head, the cavity accommodating a cartridge inserted into the upper end of the head; a cartridge percussion system into a sealed body and adapted to cause the explosion of the cartridge, and connected in a top position of the head, the explosion of the cartridge, of the blank-loaded type, causing water to be expelled laterally through the firing mouths when the device is operationally immersed in water within the down-hole.