We have a few different types of Terns on the South Carolina coast. Of course they all have a similar head marking. This bird doesn’t seem to fit though.
Note; BayPhotosByDonna cleared this up, a Forster’s Tern. See comments.
My best guess, a Sandwich Tern. This is not part of their usual habitat range though.
The black bill still points to a Sandwich…best I can tell.
Shore birds are the hardest for me to ID.
I do know it’s not a Flamingo.