A heavy blow to the head or swiftly cutting it off in one blow will instantly kill it, and is possibly the best way....if you have the guts to do it. I personality would totally freak out, and just wouldn't be able to carry through.
Sorry about your eel by the way and DON'T put it in the freezer.
Sorry about your eel by the way and DON'T put it in the freezer.
those are the two most humane ways
LIKE I SAID I WAS A KID