The AP just reported the investigation findings by Florida Fish and Wildlife Commissions on the 28 February 2009 sinking of the Fishing Boat which claimed the lives of two NFL players and another.
Read the link and the conclusion is "Improper Anchoring".
The anchor was apparently trapped by the coral reef.
On a personal note; I had an anchor do a similar thing at Anse A L'Ane, Martinique. When I tried to retrieve it after a couple of weeks, it just wouldn't budge.
I had to cut the cable.
Real shame about those football fella's, nothing humorous about that situation which lost three families a loved one.
Have a safe weekend.