A waterspout -- one of three spotted in the area early Saturday -- moved briefly onshore as a tornado on Hunting Island, according to the National Weather Service in Charleston.
No injuries were reported or property damaged, according to weather service meteorologist Emily Timte.
A spotter reported the three waterspouts between Hunting and Fripp islands at about 8:45 a.m., Timte said.
Law enforcement officials later said one of them briefly moved onto the western side of Hunting Island at about 9 a.m. before moving over the Fripp Inlet and dissipating, Timte said.
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Since there was no reported damage, it is difficult to tell how fast the spout was churning, but most typically have winds speeds between 60 and 80 mph, Timte said.
Park volunteer Buddy Lawrence was about 25 yards away when the waterspout came ashore in an area of the island where beach erosion has washed away many cottages in recent years.
"Fortunately, there weren't any nearby structures around for it to cause damage," Lawrence said. "It tore some branches off fallen trees and tossed around some sticks and drift wood. That's about it. But I turned around and got out of there because I didn't know where it was going."
The spouts were part of an active weather pattern Saturday.
The National Weather Service issued a flash flood watch for Beaufort and Jasper counties until 6 a.m. Sunday.
Scattered showers and thunderstorms were expected to dump an additional 1 to 2 inches of rain Saturday night and Sunday morning across an area already saturated from several weeks of heavy rainfall.
The weather service warned that coastal areas will be especially prone to flooding around high tide and cautioned that driving could become hazardous as high water makes some roads impassable.
Follow reporter Tom Barton at twitter.com/IPBG_Tom