Secret compartment on Navy ship

[snopes]

Comment: The ship's name changes, but I first heard this working in the
Shipyard in Bremerton Washington in 1974.

Another cool story that went around is when the USS America was built,
there was a mistake in the blueprints that didn't provide for any doorways
to be built into one of the machine shops. So, they installed a complete
machineshop, drill presses and all, and welded shut the walls around it.

A year or so later, when the ship was in service, some crewmen figure out
that there a a big unaccounted for space they were walking around and
around, but couldn't find a way in. So they got a cutting torch and cut an
access hole. Lo and behold, they found a complete workshop, with a big
sign saying, "Merry Christmas!"