Something I've noticed that always scared mew when I was younger. Maybe connected to Thalassophobia?

Well first off, like most people who are subscribed to this Subreddit have some extent Thalassophobia. I for example, can't stand pictures of open ocean, small underwater crevices, murky water where I can't see the bottom, and over all just drop offs to the never ending abyss of the ocean. However, when I was younger I never knew I had this fear because I simply wasn't exposed to that genre. I guess I was too busy playing and doing kid stuff. So let me just get to the point. When ever I would play outside and get tired I would lay down and look up to the sky. And for some reason I would always get an extremely uncomfortable feeling. Laying completely flat and looking straight up into the deep blue of the sky would give me an extremely irrational anxiety. I would always feel like gravity would just flip in reverse and then I would just fall into blue nothingness. Am I the only one whose felt this? And I feel like it's partially connected to Thalassophobia as well. I only remember this little fear I had when I was swimming in my cousins pool and I put my legs out of the water on the side of the pool and let my torso just wade in the water. I looked up and then for a split second I got that same panic looking up into the sky like I was going to fall in any second. I'd like to know your guy's thoughts on this.