to make it look really good you have to get the water as close to the edge as you can, I added a screenshot of how I did that with a barrier, then I just sit the blueprint on top and adjust the rocks so the lip of the barrier does not show. Theres some youtube videos on how to do it as well if you want to see it being done in real time

will def check this out. I never got how most waterfalls seem to just appear out of nowhere