Here in northern California, snails have been a plague since about 1865, when a Frenchman imported them for eating and they escaped in San Jose. They have multiplied exponentially for over 140 years...
So I have no compunction whatsoever about smashing their little/large selves back into MY soil, from which they have drawn their sustenance.
Method: When I'm going "snail hunting" (which is about once a week now that the rainy season is over), I water late in the afternoon. About 2 to 2-1/2 hours after dark, I go back outside with a flashlight and trowel or long stick. I smash the snails in place--either with my hiking-boot-shod foot or the trowel--when they're on the ground, I knock them onto the ground from branches and then smash them, I lift them up from plants and put them onto the ground and then smash them...repeat as needed.
We had a late-season rain the 29th of April and I killed a record 124 snails.
I've recorded "kills" of 23 and 14 snails the two times I've gone snail hunting since then.
I lost too many veggie plants to these critters in the '80s (when I was previously able to garden) to have any sympathy/mercy. Their quick, as opposed to prolonged, demise is the only mercy I show them.
That's MY veggie patch, made with MY compost and MY work and MY water, that they're trying to eat down to nibs.
Completely non-toxic method, re-fertilizes the soil, gives the (surviving) ants something to do other than invade my house. They can be legitimate undertakers, for once.
El Cerrito, CA