By Jingo its here, yes the answer to all your prayers!
How many times have you gone to your local water with a pleasant days lawful boating in mind to have it all ruined by some juvenile miscreant? Why must you witness your pride and joy that took many hours for you to build (or some Chinaman or your manservant) destroyed by some laughting snotty little stone throwing swine.
With firearms being beyond the lawful ownership and application of lawful citizens Pointy Industries is happy to offer the new shiny Expander 2000! "By crimeny tell me more!" I hear you bellow, well the Expander 2000 is a simple dart launching device that can be concealed in a handy trouser pocket and brandished with buttock clenching speed at a miscreant. "Darts, darts, is that all you wretch!" I hear your anguished cries. No not at all my fellow boat controlling obsessive. These darts are filled with a hydrogen/helium mix which combined with clever whatchmucallits and whodads will release said gases upon entry into nearby scum and villainy.
Who's laughting now as you witness nasty drunk/drugged villainy expand rapidly and unhappily, hover in mid air briefly- then explode in a most satisfying way. The process is a little messy so we can also provide gore-proof clothing at discount rates!
When the authorities eventually arrive they will find a happy lake with its lawfull boat enjoying populous tutting about the diet of youngsters these days, maybe it was to much "Soda pop" or that godless "Pop music" etc.....