wet plywood core
As others have said you need to remove wet core. Attached is a picture of the plywood core in the cockpit sole of my boat. The boat was inside in a heated dry shop for two months before we cut the skin off and started removing the core. The plywood was totally delaminated and dripping water. Wow. Interestingly due to the heavy lay up there were no gelcoat or stress cracks on the sole. The pedestal would deflect the deck when leaned on but not that much. Fortunately my surveyor caught this and the buyer adjusted the price which covered the cost of the repair.
For those interested, the repair entailed a new plywood core with the center section being sold glass. This means that in the future the sole penetrations for the pedestal and rudder post will be through sold glass with chance for the plywood to get wet.