A childhood belief about people

I used to believe, that there was a special garden somewhere, like near a beach. It wasn't really a "garden" it was like that soil though. And that if you stepped in the garden, a devil lady would come up of the ground and pull you beneath the surface, and you would die, unless this other lady, that looked exactly like her, would come and save you. (I thought this whole thing up so what comes next will seem weird.) I used to have dreams about mistaking the hero lady for the devil lady, and she would pull beneath the ground, but once she got down everything but the head, I would wake up sweating. It was a REALLY scary thing to think of.