There was a small but nagging leak that was leading to some water in the bilge. The cause actually turned out to be a nearly failed cockpit drain hose. As this is under the waterline, full failure could have been catastrophic! It also meant that in order to replace it, I had to dive under the boat and stick a plug in the drain thru-hull hole. Getting the tubing over the fiberglass involved 30 minutes of struggling in a tight space with astroglide.