Post it on the wood boat forum, lot of experienced builders who will be able to recognize the construction and point to potential issues. From the pictures it looks like a plywood
hull with solid stringers and a very thin layer of cloth fiberglass
over it. The white flakey spots are either epoxy, fiberglass
separating from the wood. Looks like varnish
but good one of the others. The black area is mold/mildew/something. Very common staining on wood that has gotten wet and not had good ventilation. If you can follow a water stain up to the deck
somewhere and it's raining a lot you have a deck
leak that could be wicking in from any place on deck near it with a fastner going though, trim hardware
etc. A good starting point is to clean everything up with soap and fresh water, something like simple green is good as it kills ,mildew and mold
. If you encounter anything that feels at all soft or spongy, STOP. call a professional.
If you can't detect a overhead or coach roof side leak. The next question is what is the weather
like? Is it cold and are you heating
the boat if so with what?
As gross as it sounds there is a good chance the water is coming from you! If its cold and you are using any heat, you need adequate ventilation, especially under a berth. Propane
heat also make a considerable amount of condensation
if not properly installed. All else failing a electric oil
register is a good dry heat source if that is a option and you are indeed in a winter climate.
regardless a post to the WBF would be a good idea, cleaning
things up and good ventilation is a must for a starting point.