There is a lake near me called Lake Yarbo that has a similar thing, it has bounced around and changed size over time. If you view historical imagery you can see that at one point the imagery over it was split from 2 different times and was on opposite sides of it
Thanks for the great example shadowdragon. I've been waiting for that Colombian lake imagery to update for years now, but it's still stuck in 2010. Finding a similar lake in the good ol' USofA where imagery is much more frequently updated is a real bonus. We can see how the floating island and the lake each help to shape each other. I'm willing to bet with so many little lakes in Florida that there are other examples nearby. Having said that I took a quick look nearby and found a few other examples, but ones not as perfectly formed.
That example in Historical Imagery which is right on the margins of two imagery sets is great.
These remind me of the ice discs that are occasionally seen, such as this one in North Dakota in 2013. I had no idea there were "dirt discs," too, and those lakes look perfect for the formation of them.