Waterfall Construction

[Bluelilly]

We are getting close to building our waterfall for our pool and was hoping for some input on contruction method. The builder has recommended using a weir for the water fall but my concern is that if we have a large rock on top of it (using as a dive rock) that we wouldn't be able to get to it to clean it out if we should have some uninvited guests such as frogs, snakes, etc. The other option that a builder gave me was to have a series of pipes getting larger to create the flow of water. We are going to have a sheer descent into the pool and it will be built with stone.

Thanks for the input!