The Santee and its tributaries provide the principal drainage for the coastal areas of southeastern South Carolina and navigation for the central coastal plain of South Carolina , emptying into the Atlantic Ocean approximately from its farthest headwater on the Catawba River in North Carolina .
The Santee and its tributaries give the main drainage and navigation for the central coastal plain of South Carolina , emptying into the Atlantic Ocean about 440 mi ( 710 km ) from its farthest headwater on the Catawba River in North Carolina .