Thanks for the link.
I read an interview with the director many moons ago, and distinctly remember him saying that the bog was filled with toothpaste. He may have been referring to a toothpaste 'base' with coloring added. In any case, it made for a nice other worldly bog.
Also, there are different edits of this scene out there. I do have somewhere a version of that sequence that has extended footage of her being pulled the rest of the way out, and then carried down a long flight of stairs by Zaltar (Peter O'Toole). I'm pretty sure it was an 'edited for TV' version. So, if you ever see this run on broadcast TV, you may want to catch that.