It depends on the resin. Many fiberglass formulas will absorb water. Some more than others. Most layups will absorb water if glass fibers are exposed (water wicks up the fibers into the layup). Some epoxy and isopthalic poly resins are resistant to water.
I sure hope not... :-) Seriously I suppose a little but I just purchased a boat that has been in salt and not moved under its own power since 2005. Lots of growth that divers cared for but the hull looks and feels otherwise to be fine...
Yup from what I understand every hull will absorb a certain amount of moisture. The amount depends on the resin used and any dry fibers or voids in the layup. Whether or not it actually becomes a problem and causes blisters again depends on the type of resins, and any contaminants that got into the layup. Yes a fiberglass pole will absorb water. Will it matter? Probably not.
__________________ "If you want to build a ship, don't drum up people to collect wood and don't assign them tasks and work, but rather teach them to long for the endless immensity of the sea." Antoine de
If I were buying, I'd much rather survey a boat that has been sitting in the water, than one on the hard.
Give them a surprisingly short amount of time and a lot of blisters disappear, or re-absorb or something, but they aren't visible.