An apparatus for releasable attachment to a fishing rod, said apparatus including: a barrel having a first end and a releasably sealed first region; wherein the first region of the barrel includes a space within the barrel substantially bounded by a second end of the barrel and a protrusion disposed inside the barrel; and a means of selectably adjusting the volume of the first region including adjusting the position of the protrusion along a length of the barrel; and wherein when the protrusion is disposed inside the barrel, it extends radially-inwardly of the barrel in a substantially transverse orientation to an elongate axis of the barrel; and a means of controllably feeding a propellant into the releasably sealed first region; and a means of expanding the propellant whereby the said expansion of the propellant causes a projectile disposed within the barrel to be propelled outwardly of the barrel via the first end.