The Massachusetts
is an old WWI battleship, but there's nothing really left of her that's recognizable (there is a plague which identifies her). She sits in about 25 feet of water right outside of Pensacola Pass and it's very hard to catch her with visibility that's better than 10 ft. Every now and then on a slack tide and calm day, vis can get up around 30 ft, but those days are as rare as hen's teeth.
The best diving in Pensacola is out a ways, but when you go out about 15 miles or more, the water is consistently good -- averaging 50 to 70 ft vis and many 70 to 100 ft days.
As mentioned the guys at MBT (More Bottom Time) can tell you about charters and such. With Pensacola being the Cradle of Naval Aviation, there are several old WW2 airplanes on the bottom of the Gulf as well as hundreds of artifical reefs and many spots of "live bottom" as its called around here. All are good dives.
The planes are hard to find, but if you can get a charter to take you, are worth the trouble. MBT has a lot of experience diving them, and in fact, has the entire prop, 50 cal machine gun, and other stuff salvaged from a sunken WW2 carrier based plane -- a Helcat I think -- in the window of their shop.
The Russian Freighter is one of my favorite dives, but the vis is hit or miss. 11 miles out, its just a giant junk pile of metal, but its been down so long its has a life of its own -- absolutely loaded with life. Several 6 ft sandbar sharks call it home. They are pretty friendly and will swim right over to you -- expecially if you have fish. They have never bitten anyone, but you occassionaly have to poke em with your gun to get them to leave you alone.
Anyway, I love diving in Pensacola. Its one of the reasons I've lived here for 30 years. Let me know when your coming and if I can help you in any way. I'll be glad to.
Here's MBT's Web site -- look around a little and you'll see the pics of the airplanes.
http://www.mbtdivers.com/