Catalina 320. Club boat and I'm the boat captain. For the almost three years we've had the boat there has been a persistent (but not all the time) leak SOMEWHERE.
The C320 has a hull liner which means there are parts of the boat that the actual bilge is under what looks like the real bilge. (hard to explain if you haven't seen it)
Anyway we have been going crazy trying to figure out where this water is coming from. Rebedded some hardware and a stanchion that was leaking. That's dry now. Drained the water tanks. Have checked the through hulls and no evidence of water ingress. Stuffing box isn't leaking. But almost everytime we go to the boat there is some water under the liner.
I don't BELIEVE there was water in the boat last winter when it was hauled out for the winter. We left it in the water this year and there is some water in the boat. Not much, but some.