Upper Ganges Blue is a medium blue with a soft, denim tone. It's unique as far as I know (if there's a dupe out there, let me know), and I suspect that it is suitable for all sorts of uses. It's not loud, so you can use it in more formal settings without worrying about it looking silly. It's different enough from other blues that you're going to recognize it among other blue inks on the page.
It is a bit of a wet writer. I used this ink in my Kaweco Sport, and I used both of my nibs with it. The B nib really showed off the color of this ink, but it was also way too wet. It would spread and bleed like mad from that nib, and I was kinda disappointed in that performance. Once I switched over to the M nib, though, the ink was much more manageable. It still looks really nice, and it's still a bit wet, but it behaves itself much better. It doesn't really spread, and it doesn't bleed through most papers in a medium nib. I'd like to try it in a really dry-writing pen and see what happens. Maybe I'll get some for my TWSBI 700.
You can see a few bloops on the image above. I was using my pen as an eye dropper, and it was running low on ink. That'll cause some drips from the nib, and once I put in a bit more ink, it worked just fine. I'm not really sold on the eye dropper pen. I'm going to be using a cartridge for a while instead. I use too many samples to be an eye dropper man, I think. It's difficult to keep the pen filled as I should.
So, what about water resistance? It's got it. As you'll see in the video below, it doesn't move much at all when you put water on it. This blue sticks around. It's pretty impressive.
Verdict: This ink is great. I want it.