Not legal ones, but there are a couple locations you may be able to "get away with it". One is Bowman's Beach on Sanibel Island (head about a mile north after entering the main beach), the other is the south end of Capsersen (head 1-2 miles south of the main beach).

Now this may go without saying, but ... do not attempt to engage in sexual conduct at Caspersen, which has a tainted history in that regard. There's usually a police helicopter that flies over the trails every day, and a couple times a year there is a sting operation where they nail several pervs looking for sex. Also if you go there be mindful of the textiles that walk down the beach and cover up or go for a swim when you see them approaching.

Also, you may want to join Suncoast Naturists based out of Venice. They take occasional boating trips to barrier islands.

There is a naturist resort (Caliente) around Tampa that may also be of interest.

Article just published this week 5/22 on seven clothing optional beaches in Florida.
Beaches are classified as "legal" or "tolerated".

http://cltampa.com/bedpost/archives/2014/05/22/7-best-places-to-be-naked-in-florida-this-summer