Salt kills snails instantly upon contact with the snails.
Snails require hydration and moisture to stay alive and when salt is poured on the snail, the moisture is drawn out of the snail, which kills the snails near instantly.
Although while the salt causes instant dehydration of the snails and near immediate death of the snails, the salt could also harm plants and soil if it's overused.
You can also use ammonia spray, Dr. Earth Final Stop and even soapy water or beer to drown the snails.
You can gather the snails up and drown the snails in a container of soapy water or even beer, which will kill the snails.
Or use That's It Snail Bait, which uses quick action through metaldehyde to kill the snails.
Dr. Earth Final Stop is an organic, ready to use spray that works immediately for killing snails as well as the snails eggs.
You can also mix 1 part of household ammonia to 4 to 8 parts of water to kill the snails in seconds without damaging most plants.
Other ways to get rid of snails are to use copper tape, Diatomaceous Earth and even Iron Phosphate Baits like Sluggo.
Copper tape will act as a barrier to snails and cause a mild electrical charge to the snails upon contact.
Diatomaceous Earth is a natural powder that dries snails out, but also requires the conditions to be dry to be effective at killing the snails.
And iron phosphate baits like sluggo are safe to use around wildlife and pets and cause snails to stop eating and die within a few days.
Even placing the snail or snails in percent ethanol for 10 to 15 minutes and then 70 percent ethanol for another 5 to 15 minutes can kill the snails.
When spraying for killing snails, you should also spray or apply any bait for snails in the evening or at night as it's when snails are most active.
And although iron phosphate is safer, some like sodium ferric EDTA, can however be toxic to pets.