In addition to the wet spots David mentioned, there are two more I've heard of:
1. This has never happened to me, but I've heard that the engine exhaust is just tabbed into the transom, straight through the core. The best thing would have been to make that area solid glass or epoxy, but that wasn't originally done. The hull was molded in two halves and glassed together, so this usually manifests in a wet transom and wet stbd side.
2. When I had my boat surveyed, the rudder was absolutely waterlogged. In my case, the seller also maintains boats, and he repaired it and replaced the core.
