The Merlin Bird ID App says this is most likely a Black-bellied Plover, or possibly an American Golden Plover. South Carolina is well within the winter migration range of both species and both sport a “black belly”  during breeding season which happens in the arctic tundra.

The sun was almost down, creating a pink reflection in the receding Atlantic surf.

The Plover came a bit closer to me as I waited watched the sun go down.