I wonder if it could have gone through cycles of buried/uncovered? I don't know anything about the waters off Florida other than they experience periodic hurricane events.
Very likely. I am in the west coast of Florida, and storms can really shift things around quite a bit. Passages between some of the small islands can open or close after a decent storm. Sandbars come and go, etc.
The waters tend to be a little deeper on the east coast, which would tend to lessen the effects of large shifts, but over a timespan of nearly 40 years it is very likely the piece had been covered over at some point.
