I have heard about a Navy base in Henderson, NV
www.abovetopsecret.com...
I would think with ships they could use an older platform to test new technology with advertising they are doing so. For instance if they want to test
a new Sonar they could mount it to an old supply ship to see what it will do without draing attention.
What about sub bases where the subs can enter the base underwater and then surface to prevent sattelites or spy planes from photographing them? Does
the US have any sub bases like that?
I know the Germans had U boat bunker bases like the ones at Lorient and St. Nazaire like this picture