Crocodiles
Just like the sign put up against the wall at that public toilet, this is similar but for crocodiles. It seems like many people who have come face to face with a crocodile have tried different ways to fight it or befriend it. Some would even go as far as to ride the large animal.
We are not sure who was the last person to hop onto the back of a crocodile and begin to ride it, but we wish there was a video of it. At the end of the day what the sign is trying to say is that you should not jump over the fence and get closer to the crocodiles.