Ok so I'm nearing the end of looking for this issue. First time we sailed the boat there ended up being diesel in the Bilge from a faulty line as well as in the lowest part of the bathroom cabinets from a hole in the aft part due to being hulled over. Today we sailed after multiple times and had a similar problem. Nasty water is in the cabinet again and the swim deck locker where the diesel tank is located. I put water tight seals on all the lockers so wherever it is coming from it's internal. To me it seems like it could be coming from the (whale raw water valve) because when the tank gets full it will leak around the top. I am replacing this part asap to be sure. My holding tank has been replaced with a plastic one a few years back. Had anyone had this issue or a similar issue? Literally it's only in the cabinet, after starboard swim deck locker, and at a point it goes into the bilge.. This is truly frustrating me.