The waters off North Carolina are often called The Graveyard of the Atlantic - more than 2,000 shipwrecks line its coastline, some dating back to the 16th century. This is likely due to the complicated geography of North Carolina’s Outer Banks (shoals, narrow inlets, small islands, etc.), naval battles, hurricanes and complex currents. A number of ships have also been scuttled to create artificial reefs. Sand tigers congregate around many of these wrecks, though the reason for this is a mystery. One theory suggests the wrecks are used as migration rest areas or navigational aids. Another theorises the sand tigers are taking advantage of the rich variety of marine life that has developed around many of the wrecks.