Abstract: An open ended, cylindrical barrel which carries a shell, is pushed into a housing until a single cam passes the position of a shoulder, whereupon the barrel may be twisted to lock it in position. A firing pin is spring pressed and presses slightly against the rear end of the shell, to hold the barrel in an outward position and also insure adequate impingement of the firing pin against the shell when the device is used. This slight pressure of the firing pin maintains the shell and barrel in an axially extended position, thereby insuring that the rearward movement of the barrel and shell, on impact with a shark or other menace, will cause the shell to detonate. The shell and housing are attached to a pole comprising a simple tube, the length of which may be varied, without affecting the use or operation of the device.