I didn't really set out to test the water resistance of these inks; I'd wanted to compare the paper in two different Rhodia dotPad No.16 notepads ordered a couple of years apart, and these inks just happen to be in pens that are on hand and ready to write.
Graf von Faber-Castell claims its inks are indelible. Well, I guess the water resistance of the three I tested here aren't bad. Even though it'd be a struggle to read what was written in GvFC Cognac Brown after a long soak, I must say what's left of the marks on the page are distinct enough to make the text legible if one really tries.
I am pleasantly surprised by the water resistance of the two Jacques Herbin inks, even if they aren't are good in that regard as GvFC. I'm disappointed to the same extent that the two Monteverde inks were washed away without leaving a trace.