Most of those are a lot more difficult to set up than you make it sound, or completely ridiculous (such as you need a machine gun, oil is much harder to light than you might think, and kerosene would probably need a rather large amount before it would stay lit on the water (and even then you could make holes easily enough), what the hell aquarium has piranhas, and I have no idea what you mean with the lock.. I don't even know what you would need access to in order to release the drain, but you would at least have to break through some padlocks to get there).
Note that half of those methods just get them to get out of the pool anyways, and then you still just have to fight them. And they probably are armed with pool noodles. A grizzly prospect if you ask me.
I guess camping with a gun would be the best option, if you had a gun handy.
Btw, I'd give maybe 40/60 odds that jumping on them would backfire. :P