Is there any fountain pen ink that won't melt in water?

It's very simple to have fountain pen ink that doesn't melt in water.

There are three kinds of ink on the market now: dye ink, carbon ink, and iron gall ink.

Dye ink will melt in water.

Carbon ink with carbon and gums, you can make the handwriting very firmly stay on the paper, even if the paper soaked in water, the handwriting will not melt. So archival records usually use carbon ink.

Iron gall ink is usually blue-black, which adds some firm handwriting things, handwriting firmness is also very strong. But iron gall ink is corrosive to the fountain pen tip.