We do not have a waterfall feature in our pond, but we do have a pump.
The pump is submerged and the end of outlet hose is hidden under stones by the edge.
Here is what it looked like a few years ago. At present due to a bit of reconstruction and the recent heavy rain the outlet is below the water level so there is just a gentle circulation of water in one part of the pond.
It is quite good to see movement in the water and at least one of the water plant appears to grow better where the water moves.
We did have a problem with newts getting killed in the pump inlet, but a bag made from a net curtain solved that one.
If you get a powerful enough pump you could easily drive a waterfall, but there is, as has been mentioned, the "problem" of getting it to look good.
Dave
Dave