just make one man! get a plastic 500ml (suggested but it doesnt matter) bottle, make a small hole 3/4 of the way down, put a tube in the hole so the end hits the bottom of the bottle and the other end sticks out, this tube can be made from a discarded biro for instance. then make another "ventilation" hole 1/4 of the way down, put water in so the end of the biro (but not the hole in the bottle) is submerged, put a spliff in the tube, spark up, cover the ventilation and breathe through the top. you know you're doing it right when it bubbles.