got the chance to play the new shadow of the tomb raider game recently and loved the mud physics in it so decided to see about recreating some form of it in unity - thought you might like to see the result
here's the mud from SotTR (at 9:43)
for anyone interested the guide i used can be found on
youtube here - i imagine it can be ported to AGK but GG would likely need some extra commands (such as creating a texture at runtime).