STOP FUCKING WITH WILD ANIMALS YOU BLITHERING IDIOT.
You don't see hikers snuggling with pumas or bears. What defect in divers' brains makes them want to get all chummy with vicious carnivores?
I swear to Christ, if they're not hand-feeding sharks or intruding on dolphin orgies, they're poking their hands in every rock crevice looking for some ambush predator to pester.
Think about it from the eel's perspective. This terrifying and loud thing has come down from the up-world, and is handing it food. Best to make a show of worship to the mysterious deity.
Cunning on the part of the eel and, once it has been established the upworlder is clearly weak, you can always take a hand as a show of power if things become uncomfortable.
Nero had a pet eel he kept in a little pool under the dining room of one of his vacation houses. He had it's gills pierced and it wore an extravagant gold eel gill-ring. He kept it for the better part of a decade, and when it died, he held a funeral for it.
The denouement of the funeral was eating it, of course. I think of this story every time I have an eel roll.