Navy construction crews have unearthed a rare Spanish ship that was buried for centuries under sand on Pensacola's Naval Air Station, archaeologist confirmed Thursday.

The vessel could date to the mid-1500s, when the first Spanish settlement in what is now the United States was founded here, the archaeologists said.

But the exposed portion looks more like ships from a later period because of its iron bolts, said Elizabeth Benchley, director of the Archaeology Institute at the University of West Florida.