I don’t know how/or if they really know but the people I saw doing it say the eels don’t feel a thing from the stings.

The downside is that eels can get really ‘pushy’ with divers and snorkelers when they are fed by people. Its very much frowned on for that reason. Now they will feed the crap out of sharks but they keep their distance. I have photographed several big morays way up close and haven’t bumped into an agressive one while taking pictures. They stand their ground which makes them good photo opportunities. I did have one swim up behind me into my fins for a bit but the irony is I never even knew it. Someone else told me after we surfaced.

BKB