As someone else mentioned in another comment, it may be a "wet bath" as found in smaller RVs and on boats. The whole bathroom converts to a shower, basically, b

As someone else mentioned in another comment, it may be a "wet bath" as found in smaller RVs and on boats. The whole bathroom converts to a shower, basically, by having all surfaces water-tight. It's a very efficient use of space, but very few larger RVs have them, because they aren't considered comfortable by some; keeping them dry and clean is reportedly an issue. I've been thinking about tiny houses for years (and I've live in a motorhome for about five years), and I think I would prefer to build slightly larger and have a nice bath and shower. But, in other regards, small is beautiful.