It also could be a fisheye in the barrier coat caused by improper preparation of the hull prior to barrier coating the boat.
A fisheye is a defect usually found in a coating, like paint or in this case barrier coat, that is caused by some oil, wax, grease or silicone residue left behind on the surface from improper preparation. It usually has this appearance:SD - what is a fisheye?
I now have them all filled but my interest is in not ending up with the same thing after I apply the additional barrier coats I'm planning on applying next. So I'm trying to figure out what caused them.