My theory is if I'm bathing in it, it's safe to put in my vag.

That's what I was thinking. I mean, "not safe to drink" to me means that it can cause diarrhea or stomach/intestinal problems, not that the water is toxic.

So what do you think about a clear, fast moving stream? There are microorganisms in there, but I would bathe in it....

I'd personally use the water from a clear, fast moving stream.

I'd probably still want to rub a little alcohol on it, regardless. I'm fine with just re-inserting my cup without rinsing during my period. I'd rather do that than potentially introduce a foreign bacteria that's going to multiply like crazy in there because I don't have any antibodies to it. Between periods I'd rub some alcohol on it after rinsing in the questionable water.

Now if it's soap + water, it doesn't really matter if the water is questionable. That's part of why it's okay to bathe or wash dishes in it-- the soap kills most of the bacteria. There's "camp soap" to use while camping, that biodegrades quickly.

This is kind of a toughie, because it's not always the case that "not safe to drink" means "not safe for anyone to drink" - sometimes it means "perfectly fine for locals who have the intestinal flora to deal with it." That said, you don't know and you probably can't find out, so for this I'd stick to bottled water. FWIW, I'm doing the same thing :)

If it's safe enough to brush my teeth with or shower in, I'd use it to clean my cup. And I wouldn't worry about the water quality in Korea honestly. I lived there for a year (in a rural area) and drank the water all the time.

I used my cup when I went to Egypt for a week--we were told not to drink the water but showering was okay, so I just used tap water. (Though that was the month where I either skipped my period or otherwise Weird Stuff Happened that may or may not have been related.) I would be leery of streams, because while microorganisms might be okay to bathe in, I don't know about putting them inside your body with nice nutrient-rich endometrial blood to munch on.

If you don't want to use bottled water, how about boiling some water and set it aside for washing your cup? I don't think the water in all three countries is that bad, and it'll definitely be potable after boiling. I wouldn't wash in a stream though, it's probably safer to stick to bottled water in that case.

If I'd bathe in it, I'd use it to rinse my cup.

well, a woman posted to the russian cup comm some time ago about her experience with a cup while travelling to "exotic" places. she used stream water a lot and she's fine :D

this is old, but in case anyone else comes across this post:
I went to Bali for a week and BC was messing with my period (like, it was going for a whole month, blah!). I washed it in tap water then rinsed it in bottled water and had no problems.

[TMI!!]
Beach sexy times have also caused me to wash it in the ocean (though as soon as I got home it got a thorough rinsing out with soap). I was pretty rapt that I could just take it out at the beach and pop it back in. Couldn't do that with tampons for sure!!