I found holes like that on one of the lifting strakes on the bottom of the 1990 Grady that I had. I cleaned them out with a dremmel and it was more prevalent that I had thought. I had to wait for the water to drain out of the laminate. I used 2 part epoxy caulk stick to fill in the holes as water would not effect the curing of the epoxy and then I sanded the patches down smooth.