I'm not sure I completely get how the "operation" worked. So you have these magic eels that are the key to extreme longevity. The facility pretends to be an elite spa/resort. The patients are given the nasty eel-water and a procedure extracts the filtered product as the elixir in the blue bottles (which the staff and other privileged people get to take to keep themselves young). The process turns the subject into a desiccated husk which eventually is disposed of as eel food.

What was the deal with the bodies floating in those chambers? Characters we saw in those chambers we would later see walking about. And we would see people physically falling apart (like losing teeth) only to look well again later. Is the idea that they're being given a little exposure to the "good" elixir so that they can be repeatedly used as human filters (and maybe they're only killed after they're "used up" after multiple procedures)? Or are they allowed to heal on their own (and everyone there must have dentures/implants/bridges for their teeth). Why does no one remember the eel treatment? That strikes me as something memorable. The main character clearly remembered ... is just more special than everyone else?

On a more day-to-day matter ... how can this place stay in business? Everyone who checks in there disappears (to become eel food in the end). And it's not like these are people who will be missed ... I got the impression all the patients were wealthy and powerful.

That was a whole lot of wedding guests at the end (presumably all of them "in on it" and having access to the youth elixir). More than the staff and even a few of the upper-class villagers. Were some of the patients in on it too? Is there some kind of world-wide elite conspiracy that's keeping this place going? If so, that seems to go against the idea that Volmer is running everything.

I know ... I'm probably devoting way too much mental effort into this movie