|No, this isn't a corner in a cave, it's the cabin bilge, and the section that's been cut out is the rusted through parts of the skintanks and their balance pipe.|
So, apart from the stupidity of allowing the shower to empty into cabin bilge, (where it flowed back to sit under the cabin stairs pooled in the pea shale ballast), it turns out that the skintanks had also been leaking into the same area. These factors caused the leak that brought about the need to re-bottom Freyja.
After we had re-bottomed her, I said that we needed to seal the holes in the old bottom and make sure that there were no pinholes around the plate that was welded over the damaged parts of the skintanks, unfortunately our welder didn't see the future potential problems and did it his way. This has caused me weeks of grief as I've chased and repaired countless leaks.
The skintank leaks to both the cabin bilge and the engine bilge seem to be fixed, at last, but I've no idea how many leaks persist between the old and new baseplates.