Fear of floating away, fear of vastness

I have this fear of floating away which is triggered by big open spaces, like the beach, or the middle of a soccer field. I get a sensation that I'm going to float off the ground. While contemplating it doesn't invoke fear, the actual feeling is terrifying! I avoid those places that cause the fear as best as I can, and am very careful and even worried about finding myself in one of those places! I have not found many others with this same fear, and have kept it secret because it's hard to explain.