We have recently had to deal with a pretty new(2017) boat from a very reputable hull and fitter, which had a water full bilge.
Trad stern, this is important.
A very well put together boat on the surface, quality everything. Damp smell and visible water under the forward cabin ballast.
....more water further back....visible damp to woodwork in galley area.
First obvious attention was to the water tank under front deck and water pumps, no leaks.
Then try bathroom, under shower inaccessible, toilet and hand basin, but all hoses seem secure, inch of water in bilge. FlexiCamera under shower sees no leak when shower running and gulper going...
2nd bedroom, over an inch of water, steel ballast over ballast bricks rusting...
We noticed straight away in the front and shower area that the spray foaming of the boat had gone down to the base plate cross members and the drainage holes had been blocked, not just one, but every one we could access, therefore any water couldnt drain back.
The kitchen area lower regions were deep in water.
Around 500 litres were taken out.
Moved the boat into the dock for further investigation.
Stern Gland impossible to access without dismantling rear cabin woodwork and metal framing, stern gland pouring in.
Previous owner said " what's the bilge?"
Basically, the inaccessible rear end has led to it flooding the boat forwards. , bit by bit.
The bilge pump worked, until someone cut the auto wire switch as it was cutting in all the time. The engine bay itself was dry, as the cocooned engine and drip tray was installed above the bilge, so nobody thought the cabin water was coming from the back.....it was slowly going forward under the hidden areas.
The company involved said there was no fault in their fitout.
I suggested that blocking bilge drains in at least 6 visible (the only visible drain holes) areas with sprayfoam was not good practice. No response yet.