Florida has far and away the most good clear water diving in the world due to its geography.
http://www.ginniespringsoutdoors.com/
Ginnie Springs is one of the most celebrated of the Florida springs. Ginnie has a wonderful cavern dive that is a must do.
http://www.divebluegrotto.com/indexflash.html
Blue Grotto is close to Ginnie so you can plan to do them both while you are in Florida.
I have been to these several times and would highly recommend them to anyone. I will be there for a few dives next month. We like to take students there for check out dives.
http://underwaterflorida.homestead.com/manatee.html
Mantaee Springs is another good dive with the possibility of spotting a manatee on any given day. I myself have never had the pleasure of running into one there yet.
http://www.florida-scuba.com/Crystal_River.htm
This is the spot for Manatees, and while the river water is as crystal clear as any water in Florida, often the water is stirred up by the many people that may be there on any given day. There are places that are better than others. Call and ask some questions, tell them your needs and I am sure you can find a great spot.
http://www.americanprodive.com/info/Rainbow_River.asp
Wonderful drift diving and perfectly clear water. A good experience but not a lot to see.
Good luck and happy diving.
