Most times, this kind of cracking is purely cosmetic and doesn't indicate structural problems, at least not yet. Gel Coat is not a structural material. Gel Coat to fiberglas is what the candy coating is to the chocolate inside an M&M. It's put in the mold to give the fiberglas a shiny aesthetic. The new boats made out of carbon fiber or vinylester resin and vacuum-bagged don't even use gel coat in the way we have once known it to be. That being said, however, if enough gel coat cracks, then water will definitely seep inside creating more problems as the boat ages. There are a number of fixes for this problem and none of them are quite as aesthetically pleasing as original manufacture unless you plan to paint your hull. What I would do, and I agree with both Steve and David in their comments about checking into the problem, is to have your yard look at it next time you have your bottom done, provided you don't find evidence on the inside of your boat that something going on inside is creating the spiderweb cracking outside. Typically, this doesn't happen. By the time something inside manifests itself outside, you have much bigger problems than spiderweb cracking.
