One day, there was a fire in the jungle; in order to escape from it the animals had to cross a large, fast flowing, river.
This posed no problem for the larger animals. However, it proved to be an insurmountable obstacle for the frog and the snake; if they attempted to cross it alone.
However, if they worked together; whereby the snake would carry the frog, and the frog navigated, they would succeed in crossing the river.
The snake was the natural enemy of the frog, as he (the snake) regarded the frog as a food source to be eaten on sight.
However, they worked out a bargain whereby they would aid each other in crossing the river.
All went well at first, the frog sat on the snake's back and they entered the river.
They reached the halfway point, then the snake flipped over onto its back, and tossed the frog into the air; so that it could eat it in one go, as it fell back down towards the snake.
The frog exclaimed:
"Why are you doing this? You will drown if you eat me!"
The snake replied:
"Because it is my nature".