After some research it looks like a liveaboard is pretty much the only way to really dive Dry Tortugas. There are a few dive ops with fast boats that'll make the 140 mile round trip just for a day excursion, but from everything I've read they just get you to the outskirts. I might have to look into the liveaboard option in the future to really experience the area.
According to the interwebz, knower of all that is true :lmao:, Dry Tortugas is an unincorporated area of Monroe County, Florida and it is part of the Lower Keys Census County Division. Key West considers it their 'baby' from what I understand.