I like to do the Waterfall by entering it like a tail slide. Do it high to start. I pull vertical at a low power setting. I use only a click or two of throttle to give the tail authority for corrections. The plane will slow to a stop and then try to tail slide. The instant I see almost zero airspeed I push 3D down elevator and give power. At the point where the plane is almost stopped (not actually motionless) it becomes weightless for a moment and will waterfall much easier than from a hover. Check the CGs and throws and just keep on flying. I've seen many ways to Waterfall. It looks good immediately following a Wall. I once saw a Roll to inverted, followed by what looked to be the first 1/4 of an outside loop the Waterfall. I love to do the Waterfall I first described here, just following a vertical takeoff. That usually gets a wow.