what about a swamp?
 

Do the Florida Everglades, or any swamp land for that matter, count as a body of water in which flotation devices are needed if flying further from gliding distance to the shore?

To my knowledge, there is no requirement for a light aircraft to carry flotation devices. (Please correct me if I'm wrong... it's been a while since I've flown a 172). Is it prudent? Heck yeah.

What I can find is the following reg, which applies to large and turbine powered multiengine aircraft:

Seeing that in the everglades and other swampy areas, you're almost certainly going to be within 50 miles of some sort of suitable landing site (highway/airport/beach/etc), I'd say no.

If I was flying a light aircraft over the everglades, I'd be more concerned about carrying the appropriate post crash survival gear (such as an Personal Locator Beacon), than a life raft. Odds are that if you go down in a swamp, it's not going to be very deep and "ditching" efforts are going to be a combination of an actual ditching and an off airport landing onto uneven ground due to the dense vegetation that you'd find in such a location...

My personal recommendation when flying a single piston over such locales? Stay within gliding distance of a major highway or other suitable road. That way if you have any trouble, you know that help is there right away. It might add some time/cost to your trip, but if you go down into the swamp, it could be hours or even days before somebody finds you.