FIG. 7 shows an air cannon system loaded with a launch canister containing a prop-fouler. A pressure vessel (28) contains an inlet including a poppet valve (100) that, upon command, can be selectively placed in either a one-way flow position to permit charging of the pressure vessel or otherwise opened to trigger rapid discharge through pressure equalization with the ambient environment. The air cannon may include multiple splayed barrels or a single barrel (158). A launch canister (202), realized in the form of a tube, has a driving plate (350) that closes an end of the launch tube. The driving plate is the first point loaded into the barrel. Within the launch canister (202) a first portion of a floating prop-fouling line is stored. The prop-fouling line, such as made from Dyneema®, has at its ends two drogues that, upon entry into the water, fill with water to produce drag resistance to movement of the prop-fouling line. To avoid undue stress on canopy panels of each drogue and to avoid twisting of shroud lines (312) to the canopy, a rotating shackle (310a, 310b) acts as a coupling point between the shroud lines (312) and the prop-fouling line. Only one drogue (306), its associated coupling and a selected length prop-fouling line are loaded into the launch canister, with the other drogue and its rotating shackle (310b) loaded into a cradle (166). Upon firing, gas expansion causes the rapid acceleration and ejection of the launch tube (202) and generally straight line deployment of the prop-fouling line (302).