So the little lizard climbs up and sits next to the koala and they have a few joints. After a while the little lizard says his mouth is 'dry' and is going to get a drink from the river. But the little lizard is so stoned that he leans too far over and falls into the river.
A crocodile sees this and swims over to the little lizard and helps him to the side, then asks the little lizard:
"What's the matter with you?"
The little lizard explains to the crocodile that he was sitting smoking a joint with the koala in the tree, got too stoned and then fell into the river while taking a drink.
The crocodile says he has to check this out and walks into the rain forest, finds the tree where the koala is sitting finishing a joint, and he looks up and says "Hey you!"
So the koala looks down at him and says:
"Dude... how much water did you drink?!!"
[hat tip to WR and JB of Lousiana]