Oh thank god: Mystery
Oh thank god: Mystery of Black Water off Florida Solved. (The italics below are all mine:)
A mysterious patch of black water off the Florida coast, the extent of which was detailed by satellite images, is most likely the result of a bloom of algae...
...A scientist with the Florida Marine Research Institute, said the black water bloom does not appear to be hazardous to humans, adding that the event is not likely the result of polluted river runoff or any other human or mysterious cause...
The latest satellite imagery indicates that the discolored water seems to be dissipating, the researchers said.
Well, then. Glad that's all cleared up.