So... working on my sandfall. Did the main body of it last night, and the cement is drying right now. Here is the work so far
The foam part. I filled in the back and let it dry some bafore laying the hose in, otherwise it sunk in.
After it dried i cut slits in the foam and put the rocks in
Then i coated it in cement. I sifted the rocks out first.
The "pool" design has changed since i took the pic, but you get the idea