I had those when I had the hull sandblasted to remove all the old paint … millions of them, but even smaller than an eraser head. None were deeper than just penetrating the gel coat. Also they were dry. At no point between sandblasting in the fall and applying barrier coat did these little pin pricks weep any kind of liquid. The protocol that I used was to apply an epoxy putty to fair the surface. Then I applied 3 coats of epoxy barrier paint. The paint alone will not fair the surface smooth. It was expensive. It was $1,900 for the fairing alone. I spent $4,200 altogether to make the bottom into what I wanted - between the sandblasting, fairing and 3 barrier coats of paint. Before sandblasting, I had very rough surface from years of paint that didn't slough off. Now, the bottom is smooth and I'm happy going into my third year with the bottom repaired. This for 27' boat.
All that said, I can't tell what you are showing. Is that a painted bottom or are we looking at bare gelcoat. To me, it looks like those holes have already been faired. Are they smooth or are they divots. Honestly, the photograph doesn't seem to show any divots, it looks smooth to me (but perhaps the photo is deceiveing. All the spots look like divots that have already been filled to me. But I don't know what you have done for preparation so far. Anything? or is that the way it looked when it was in the water?
My hull was covered with old paint that couldn't be scraped off. I had no idea that all the little divots would be exposed when I had it sandblasted. There was no indication that there were any blisters through the paint or that blisters would appear after sandblasting. However, the sandblasting took off all the paint and roughened the gel coat. All the tiny divots were gelcoat that was popped out - as if there were millions of gelcoat divots that were loose and ready to be sandblasted out. There was no delamination or contamination of the underlying fiberglass.
