There are blackwater rivers all over Florida that will be very similar to what you'll find in Central and South America. I'd spend the winter scoping out some different spots and don a mask and snorkel when it warms up a little and give it a peek. The Peace River is a great example. You can also fossil hunt as well as collect some great driftwood. When I was a kid, I had a bunch of cypress driftwood that I wish I would have held on to. You'll probably be able to get some plants as well.*
*I am unfamiliar with collection laws in Florida as it relates to anything above. Research at your own risk.