"They're here," said Mel Bell, director of fisheries management with the S.C. Department of Natural Resources.
Carlos Chacon, natural history manager at the Coastal Discovery Museum, said he has spotted more than 15 Portuguese man-of-wars washed up on Hilton Head's beaches during his 13-mile morning sea-turtle patrols.
They typically show up a few times each summer when they get stranded by winds and currents, Chacon said.
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"It's not like the beach is packed with them," he said. "But it's more than usual."
A ranger at Hunting Island State Park said no Portuguese man-of-war sightings had been reported at the park's beach.
The Portuguese man-of-war, Physalia physalus, is not actually a jellyfish but a siphonophore -- a distant relative of jellyfish -- which is a colony of cnidarian animals.
Its pretty colors tend to attract people to the creature, also called "blue bottle jellyfish," when they don't know what it is, Bell said. His daughter as a young girl picked one up once on the beach when he was turned away, and told him to look at the pretty balloon. Luckily, she grabbed the float rather than a tentacle.
It's unusual to find the tropical man-of-wars near Lowcountry beaches, Bell said, but "when the winds are right, stuff just blows in from the Gulf Stream."
Man-of-wars can't swim; they "sail" on winds and waves. They sometimes are found in clusters in the Gulf of Mexico but usually are floating by themselves when found in the Lowcountry; they disperse as they drift. Here or in the Gulf, "I've never seen them as thick as other jellyfish get," Bell said.
If you see them, stay away, Bell cautioned.
If you find one on the beach, you should bury it without handling it so it doesn't sting anyone, he recommended.
Even stranded, its long tentacles can still sting. More venomous than jellyfish, Portuguese man-of-wars leave marks that "look like you got whipped," said Shore Beach Service operations manager Mike Wagner on Hilton Head.
If beachgoers suspect a sting is from a man-of-war, they should keep an eye on wounds and seek further medical attention if symptoms get worse, Wagner said.
Packet and Gazette staff writer Allison Stice contributed to this report.