We discovered our accommodation bilge of our shared narrowboat to be full of water when the carpet in the cabin became very wet, on lifting the carpet it was discovered the flooring was saturated and rotting away.
The culprit was a leaky water pump under the concealed under bathroom sink.
Requiring the floor and everything built on it needed replacing up to and including the bathroom.
Having never been happy with the quality of the original fit out the owners elected to have a full refit and pay the difference between our insurance settlement and the cost of the refit.
We had no inspection hatches and will have them installed in the refit.
Hope the source of your leak is less expensive