Almost looks like they over foamed it during construction and popped the seam. I doubt much water got in there. That is an easy fix because you don't have to be especially neat. Feather the edges out lightly an inch on each side with a grinder and use about a two inch wide strip of thick biaxial cloth and epoxy resin. Grind and clean, cut the cloth to fit, mix resin, wet seam down, lay up the cloth, wet with more resin until it is wet through, let it dry. Done. Epoxy is more costly than fiberglass but in this case it doesn't take much and will stick much better and is far easier to work with as it has almost double the working time of fiberglass.
Last edited by blackcreek; 10-25-2013 at 11:07 AM.