In the battle of Helms Deep,the Urah Kai come to the front of the wall.They are holding torches.Then it starts pouring.How come the Urah Kai's torches are still burning?Maybe it's Greek Fire?{For those who don't know what Greek Fire is,it's fire that can't be put out by water.}
The torches in the keep with the Rohirrim don't go out either. And they are torches; torches are dipped in oil, tar, pitch, etc. These things don't go out in water.