Which side is the leak appearing? If it is on port side the fixing screws for the plates holding the swim ladder in place could be the culprit. Would be entering when sailing, or doing a lot of bathing! Also as mentioned if you have the aft rubbing strake bolts might be leaking at the lower end. These are normally above the water line and would not leak unless extreamly laden or actually sailing.
Then there are the rudder post, which comprise a SS tube fibre glassed into the hull and do not have any packing box but will not leak unless sevely damaged by inpact to the actual rudder. That you said has never happened and if so also would mean water ingress into the engine compartment.
I had fresh water in the same compartment on port side from a faulty fitting on the shower
tube above the engine compartment.
Would be interesting to hear what caused the ingrss once you find out.
Happy lead free sailing from Lucky