This pic is definitely a croc and not a gator. Also the flora in the background is not what is found around Lake Placid, Florida.( mostly open fields, large oaks, cypress stands. Typical central Florida type terrain.)
There was another set of pictures circulating the net recently, an extremely large gator swimming across a lake with a whole deer in its mouth.
This email stated the picture was taken from a helicopter while flying over lake George, east of Ocala National Forest, and north of Astor, on the St. Johns river chain of lakes.
A second email about 2 months later showed the same pics, but stated they were taken over Lake Placid. This time they also included pics of a game commission employee standing next to the deceased gator while hanging from a large tree. Claimed the man was like 6'4". This made the gator appear to be like 18-20'.
I have a friend that lives on the SE side of Lake Placid, The pics actually looked like they could have been taken in his neighborhood, although he doesn't recall hearing anything about it. So I guess you can take it how you want.
If I can find the pics of this event I'll try to post them.
In the mean time, that's not a gator, and it is highly unlikely that it was taken around the Lake Placid area. I also vote Australia!