Let us suppose, dear reader, that you are worried about small drone aircraft -- copters, quad and hex and so forth - espying on your private activities. This is not as completely unreasonable a fear now as it was a few years ago. A realtime first-person-view drone can be as small as your hand and still manage 10 minutes of hovering and scooting about.
Let us also suppose that you are not the sort of maniac who is willing to shoot a deadly projectile at a rapidly moving small target in a populated area. If you are that sort of maniac, please move to an unpopulated area immediately, and put up big signs at your property border. "I am an armed idiot" might be suitable phrasing.
So, what are the characteristics of a suitable solution? We want to stop a device which is small, fast, unpredictable, and lightweight. It is guided by a human (likely to remain true for the next 20 years, when AI will replace us) who has an OK field of view straight ahead and down a little.
- we could use an energy weapon
Archimedean solar reflectors would be cool, but aiming is a problem, as is the availability of sunlight. Lasers are great, except that their focal distance causes them to have somewhat excessive ranges. Blinding an aircraft pilot by accident is not a great outcome.
It would be nice to use a jammer to remove the video and perhaps control interfaces linking the drone to the pilot. Sadly, the FCC frowns on jamming. This is a tactic that the military could use, perhaps.
- we could use a projectile weapon
Yes, let's throw something really fast at the drone. Bullets are out. Anything resembling a bullet is also out - shot from a shotgun, marbles from slingshots, rocks from slings, arrows and bolts from bows. These all share the problem of continuing to be dangerous after they miss the target. We'd like to avoid that.
And we will miss. We will miss a lot, because we are not going to be practicing every day, and we probably will not want to buy a thousand drones to let us go target shooting...
- we could use lots of projectiles
It would be nice, but not a firearm. We want the projectiles to become non-dangerous if they hit something we did not mean to destroy. Maybe rock salt in a shotgun? Apparently the range is awfully small. Something else that breaks up over distance, but retains enough energy to swat a drone 40 or 50 feet up... something like water.
A garden hose does not have the pressure we need -- well, not the pressure as such, but what a pump engineer calls "head" -- the vertical distance that the pump can raise the water stream. Your garden hose is probably good for about the height of your house. Not good enough.
How about pressure washers? You get a tank, a compressor, and a hose with a nozzle tip on it. Some of the high-end pressure washers come with their own gasoline engines. They cost from a few hundred to a couple of thousand dollars. And all of them seem to assume that you can stick your nozzle right up within a foot or two of your target. That might work.
What you really want though, is something more like a fire hose, with a fire pump to push a lot of water high into the air.
Turns out they sell them on ebay. The low end systems are designed for protecting your home -- that would be exactly what you want. $600 on up to the thousands. Easy to aim. Non-lethal. Death on drones.