I have a waterfall that falls into a large pond--man made. The pond is about 5 ft deep and has steep sides. Every dog that has ever visited has fallen in--once. I keep a close eye on it especially with new dogs or pups but generally one dip is enough. My current pit has fallen in twice but not for the past year.
A problem right now is the ducks. Mating pairs find their way to the pond and the dogs go crazy chasing them. I love the waterfall and pond when they are clean and working but there are frequent cracks and cleaning to deal with. Although the sound of it is great for blocking out city noise.