RedactedNarrative: THE HOVERCRAFT OPERATOR TRAVELLED ACROSS THE FROZEN MISSISSIPPI RIVER AND STRUCK A TREE WHICH WAS LOCATED ON AN ISLAND.  THE HOVERCRAFT CAME TO REST ON THE BANK OF THE ISLAND, PARTIALLY ON SHORE AND ON THE FROZEN RIVER.  OPERATOR WAS EJECTED FROM HIS SEAT AND STRUCK HIS HEAD ON THE TREE, SUSTAINED FATAL HEAD INJURY AS A RESULT OF THE CRASH.  CORONER ADVISED THERE WAS LIKELY A MEDICAL EVENT THAT CAUSED OPERATOR TO PASS OUT PRIOR TO THE CRASH CAUSING THE HOVERCRAFT TO CRASH INTO THE TREE.