Ever since we bought our boat, new, as original/only owners, it has had a strong, sharp, ammonia-like odor in the lazarettes, in the storage areas behind and under the salon seats and under the galley sink and head sink cabinet. It is not urine. We have a saildrive, so theoretically there is no water under interior sole boards. Small amounts of salt water appear every once in a while in the compartments under the sole where we store things but we can't figure out or see where it's coming from. In fact, rather than water, what we find most often is great big dry salt crystals. All the storage compartments have limber holes connecting them. The odor cannot be detected, even by me, aka "Super Nose," in the cabins or salons unless I open a storage space. My husband cannot smell it at all. The only possibility I can find online is coolant from the fridge or freezer, which is supposedly ammonia nowdays. Our freezer did just die recently. But, it has been running pretty much constantly since we bought the boat. Our boat was built in France, not the US.