That looks like it was done the old-fashioned way.
1) Type out words and print out on injet printer
2) Drip water onto printout
3) Let dry, then scan back in.
Not a plug-in, but a separate program, Corel Painter has about the best "natural media" painting, that I have ever seen. With Watercolor, one has so much control, that it is astounding.
Though PS and Painter have moved closer and closer together, for many Images, I could just not live without Painter.
Maybe Alien Skin, or others, do have a more natural Watercolor Filter?