How big is the entrance to the cave/ the river? If you could do something to seal off the entrance of it he would eventually suffocate and you wouldn't have to worry about fighting it. (I know Green Dragons can breather underwater but eventually it would use up all the oxygen in the cave...
This place isn't dead? Weird. Hey whatever happened to that Magazine -- Asgard? I can't seem to find it anywhere and I couldn't stand to have my work go unnoticed. I demand that you reinstate it immediately, or at least the cartoons. They were the only reasons people downloaded it.