1/10/14 EDIT: The map image has changed since the images were taken. A revisit is planned.
So I'm completely obsessed with these "roads". The typical trend is to build houses on slightly higher grade for drainage, with the roads receiving the runoff and transferring it to a retention pond. Since these roads haven't been paved, the rainy season render them into canals. The flag is there to indicate where a man hole will be, or maybe there's already one there and it's covered by water.
I also got to see a snake swim across one. It was too far away to identify it but this being Florida, I'm not going on a snake hunt.
There was also this seemingly random fence separating the plots.