Our in-progress fiberglass pool was not set level and as a result has so many gelcoat cracks that I can't even count them all (I've tried). Here's the thread with all the gory details:
We are in the process of sending a formal letter to the builder demanding that he replace the shell (and install it properly this time). Given his behavior thus far, I wouldn't be surprised if he continues to refuse. But if we go to court and he loses, the judgement will likely be significantly higher than it would cost him to simply fix his work now, so you never know... he might have a moment of business clarity and come to the realization that not only is it the right thing to do ethically, but also financially.
Anyway, one thing he's said several times is that all fiberglass pools have gelcoat cracks. Not necessarily to the extent that ours is, of course, but the context of this comment has been "...so when the new shell goes in and ends up having a few cracks too, you're going to demand that it be replaced again." The manufacturer's warranty literature mentions the likelihood of cracks as well, by saying "...it is impossible to prevent the gelcoat from developing hairline cracks... gelcoat is prone to develop hairline cracks as the earth shifts and settles or while the concrete expands and contracts."
So, I suspect that if he does agree to replace the shell, he's going to want some kind of agreement that we'll accept the replacement shell even if it has a few cracks.
I don't find that entirely unreasonable, particularly if the shell is installed carefully and level this time and "a few cracks" is clearly defined. But I have no frame of reference to know for sure. Are gelcoat cracks really common, to the point where it's unrealistic to expect a shell that is completely free of cracks? If your pool has gelcoat cracks, approximately how many and when did they occur (at the time of installation, or months/years later)?