S.C. Code Ann. § 50-23-5: Watercraft defined.

For purposes of this article, as it relates to the taxing authority of county officials, "watercraft" means anything used or capable of being used as a means of transportation on the water, including any affixed outboard motor, but does not include: a seaplane regulated by the federal government, water skis, aquaplanes, surfboards, windsurfers, tubes, rafts, and similar devices or anything that does not meet construction or operational requirements of the state or federal government for watercraft.