I finally know what 'sky squiggles' are!
I have been wondering since I was a kid about the hundreds or thousands of semi-invisible 'sky sperm' or 'sky tadpoles' or 'sky squiggles' that you see swimming around in front of your eyes if you stare at a bright blue sky. Some people will try to tell you that you are simply seeing floaters (what some might call 'sky amoebas' or 'sky worms') and that it couldn't possibly be anything else, but thanks to the Internet, I found out that it's called blue field entoptic phenomenon where you're seeing your own white blood cells:
It's nice to finally know the truth.
Note: This is not the same as floaters. Below are some images of what floaters look like with links to where the images came from. Floaters move slowly across my eyes, but white blood cells are small and really fast.