Re: Blisters, OMG
My boat just had her 50th birthday. No sign of osmosis in the hull, but a few small blisters are in the fiberglass that encapsulates the keel. They can stay there.
My sister has a fiberglass swimming pool which is now about 40 years old. Because where she lives it never freezes, the pool never gets drained in winter, so has never dried out or been treated in any way. It has had two or three quite large blisters in it for as long as I can remember, but they have not got worse over the years.
I favor doing nothing unless delamination is occurring.