This is what happened to this poor dog in the video below. It seems that he got stuck in a spillway full of water. For the unlucky guy is simply impossible to get back up the slippery slope that got him there in the first place.
Fortunately for him, some teens saw him and formed a human chain to get the dog out of there. He was lucky to be seen and to have gotten the help he needed. That was quite a day even for a dog. Not every human would bother to safe a dog, so a big up goes for those teenagers, well done.