The GW stuff is just varnish. Dont buy it. You have to pour it in a bunch of really thin layers.
I heard woodland scenics is ok, but it\'s basically like a plastic you have to melt and pour, if I recall correctly.
The only water effects I really like is a two part resin that I found in the floral section of my local craft store. It\'s intended for putting in vases of fake flowers to look like real water. I forget the name of it, but it will come to me in a while.
I have a scenery piece that has this water effects, I will upload a picture in just a moment.
-Matt
EDIT: The stuff is called \"Everlasting Elegance\", and I bought it at a michaels craft store. You can see it here: http://www.michaels.com/art/online/displayProductPage?productNum=fl0010&channelid=
Here are some pictures of my terrain piece that used this, as promised!