Apparently it's real, because after a search I was able to find one other photo of a similar starfish, listed as Daytona Beach 2004. Photo credit for this one to TheMarque.
See also this sea star.
Addendum: A hat tip to Mnkyfuc for identifying this as Astropecten articulatus (described as "very common" at 20-30m depth on the continental shelf off Charleston, S.C.). More pix at the link.