If you want to go snorkeling, you would most likely have to go to Northern Florida. Tom Barr holds something called "plant fest" almost every year somewhere near Gainesville and other parts in Northern Florida. There are tons of nice, clear, plant filled rivers up there. Tom also has a subsection thread/forum on his website/forum about this.
You could collect the same plants down here in 'SoFlo', but I wouldn't suggest snorkeling in freshwater here.
Hope this helps.