Through the Authority the State may engage in promoting, developing, constructing, equipping, maintaining and operating the harbors or seaports within the State, namely Charleston, Georgetown and Port Royal, and works of internal improvement incident thereto, including the acquisition or construction, maintenance and operation at such seaports of harbor watercraft and terminal railroads, as well as other kinds of terminal facilities, and belt line roads or highways and bridges thereon and other bridges and causeways necessary or useful in connection therewith.