I find it deplorable that some of my neighbours drown cats. Yes, we have a major problem with stray and feral cats in our area, but that doesn't mean that you have to take matters into your own hands by drowning them!
Some of them trap the cats, then either leave them in the traps or put them in bags. Then they submerge the traps or bags into buckets or ponds. When they are sure the cat is dead, they pull it up, dump the body and reset the live animal trap.
It disgusts and infuriates me. We have a problem with cats, yes. That doesn't mean the best resolution is to drown them. Did you know it is considered Animal Cruelty and illegal? Pffft ... not like my neighbours give a darn about that!
Did you know, barn cats eat your mice? I have heard all sorts of excuses from farmers and I would like to say for the record ... No, the cats don't eat your chickens. No, the cats don't eat your eggs. No, the cats didn't cause your tractor to stop working. Those are the mice, rats, 'coons and fishers! Did you know that most barn cats will actually eat the mice, rats and fishers in the area?
Now, the raccoons ... that's another story. The cats won't deal with them - you'll have to figure that one out yourselves (legally and humanely).