This National Geographic video details many aspects of the Ohio Class USS Pennsylvania, SSBN-735, the largest submarine in the US Navy.

The contract to build Pennsylvania was awarded to the Electric Boat Division of General Dynamics Corporation in Groton, Connecticut, on 29 November 1982 and her keel was laid down there on 10 January 1984. She was launched on 23 April 1988, sponsored by Mrs. Marilyn Garrett, and commissioned on 9 September 1989, with Captain Richard M. Camp commanding the Blue Crew and Captain Lee Edwards commanding the Gold Crew.  Click graphic for larger view.

Ballistic Missile Submarines, or "Boomers" for short, are "lone wolves." They are designated with  "SSBN" in their name.  They disappear into the ocean, purposely staying hidden, to do reconnaissance and peace-keeping. They carry Trident nuclear missiles (for peace-keeping) and some torpedoes (for self-defense). They are huge (2 football fields long and 3 stories high), but slower and not as agile as the SSN class fast attack subs.

There are two crews, designated as "Blue" and "Gold."  The crew is larger than an SSN and more space is available for moving around (for instance, there's no racking amongst the torpedoes and little hot-racking). Their cruises are shorter than attack subs' (3 months), but they remain underwater constantly. The only communication with families is via short emails whenever the sub surfaces to communication depth. Their "at-homes" are longer though (5-6 months) making it easier on the personal life.  Guided Missile Submarines are essentially boomers which have been outfitted to also transport and deploy special forces personnel, and will support ground warfare.  They are designated with "SSGN" in their name.

28 minute video