Authorities in Massachusetts are warning swimmers about Portuguese men-of-war that have been spotted on Martha's Vineyard.
The Edgartown Parks Department said in a Facebook post Thursday morning that the marine animals have washed up on South Beach.
"Please be aware we have reports of Portuguese Man of War washing up at South Beach," the Facebook post said. "Swim with caution."
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The Portuguese man-of-war has a sail-like structure that enables it to float and long, dangling tentacles with powerful stinging cells. According to the National Ocean Service, man-of-war stings can be painful and cause welts on skin.
"I didn't know we even had those in New England," Tanya Nastasi commented on Facebook. "I remember them beign everywhere in Florida as a kid, but not here."
"Ugh go away," added Colleen Pickwick.
Experts say beachgoers should be careful because the animals can sting weeks after washing ashore.