S.C. Code Ann. § 54-15-190: Boats used for pilotage; identification.

All boats used for pilotage at Charleston, Port Royal, and Georgetown shall be used exclusively for pilotage, except that the South Carolina Commissioners of Pilotage may grant temporary permission for those other uses as they deem appropriate. To establish their identity, all pilot boats shall fly the international code flag P by day and regulation pilot boat lights by night.