[Mariner]

"How are these things armored?"

They are not. No modern ship is.

They are compartmentalized. A 500lb explosive, if it hits, can take out the superstructure of most modern vessels.

They are designed to fight at sea from dozens to hundreds of miles apart...

However, a BB can take a hit from anything but a nuke a keep on pumping 2000lb shells at the beach.

[Eric in the Ozarks]

This is a ship that could be built on the Great Lakes.
we have the shipyards in Wisconsin, etc.