Drowning them is the quickest way. Shooting them often ruins the cage when the bullet passes through and cuts a cage wire. And they don’t always die right away, even after being shot several times.>>. You are not drowning them. You are teaching them to swim. My dad did that with the local squirrels.
Not to mention, passers-by really want to see what you’re up to fly-fishing in the middle of a pasture or hay field??