From Jones Beach to Montauk Point, beachgoers encountering venomous Portuguese man-of-wars should beware: Even when washed up on shore -- alive or dead -- the animal's tentacles can cause a jolt of pain.
The man-of-wars, normally found in warmer waters, began showing up here at the end of last month. What brought them "is a combination of wind, waves and current," said Bill Wise, director of New York Sea Grant. "They tend to clump together in groups. There may be a couple hundred in a group. If the wind persists long enough from the south, it might wash most of them up."
Three people, including two children, were stung Tuesday on Fire Island. On Saturday, the fourth annual Fire Island Ocean Swim is being held on the barrier island, starting in Atlantique.
Southampton Town trustee Ed Warner Jr. was stung in Florida when he was a teen. "They're nasty," he said. "It left a mark on my leg that stayed for a number of years. It was like a tattoo."
A man-of-war is not a true jellyfish, but a siphonophore -- a collection of organisms that includes a bladder and tentacles that can reach 30 feet. The bladder part floats above the water and looks like an old warship.
"If you see a man-of-war, you kind of want to get away from it," said Dr. Sanjey Gupta, chief of emergency medicine at Franklin Hospital in Valley Stream.
"It can cause an injury that looks almost like a whip," Gupta said.
Jellyfish stings often are treated with vinegar, but Gupta said that could worsen a man-of-war sting. If you are stung by a man-of-war, here is his advice:
Remove the tentacle using a towel, stick or other utensil -- not your bare fingers. Clean the wound with seawater, not freshwater, which Gupta said could spread the toxin. Be sure not to get sand in the wound.
Once the injured area is clean, soak with warm water for 15 to 20 minutes. Freshwater can be used at this point. The pain should stop within an hour.
Seek medical treatment immediately if you experience difficulty breathing or have chest pains, a serious rash with hives or severe muscle cramping.
This week, state park officials had reports of one Portuguese man-of-war at Jones Beach, one at Robert Moses and two at Montauk. Other sightings were on Fire Island and at Sagaponack.