In all probability...
it's just gel coat crazing...not a structural issue...just cosmetic. If you want to fix it, the common way to do it is to take a can openner (do they still sell those triangular can punchers?) or something like that and run it along the crack to widen it and make it V shaped. Then fill with gel coat repair.Here's a tip, follow the curing instructions on the can to the letter, some gel coat will not cure properly while exposed to oxygen.After it has cured, take a utility knife blade and cover the sharp tips with masking tape, then use the blade to scrape the new gel coat almost down to the level of the old gel coat, then sand...saves tons of time.