All of our waterfall models look like stacked boulders so adding other boulders on the pool edge or nearby enhances the natural look. Notched Boulders have an extended lip of about 9 inches so when they are mortared to a concrete or fiberglass pool it appears the pool was built around the boulders. Standard boulders with a flat bottom are available for vinyl liner pools or landscaping. Several of our dealers are quite creative using the boulders for other applications including fire pits and spa surrounds. Submerged boulders are a special order item but they work well to mark the edge of a reef step.