Keeping dirty water in the cooler that drains to the bilge sump to maintain your cold beer? :-)
Actually, it may be the hidden bilge - look where the bilge pump hose runs aft and see if there is evidence of the hose breaking down.
That was a problem on Rhapsody and other J/30s as reported on this forum.
Mark Rotsky (Nemesis) and I have started using a long drill to put some holes from aft of the center bilge section into the hidden bilge. I got brown slime and have used wicking material and heat to draw the moisture out when the boat is on the hard. I put corks in the holes for the sailing season. This is a temporary fix until I ultimately tear apart the hidden bilge and properly fix that area.