Updated 4:45 pm
The Edgartown Parks Department is warning swimmers to be aware of Portuguese Man of War sightings.
The parks department posted the warning on its Facebook page on Thursday, along with a photo.
The sea creatures, often confused with jellyfish, carry a venomous sting, according to the National Geographic website.
Man of war float up from sub-tropical waters to the Cape and Islands. Their bodies have a cone-like shape that sticks out of the water and is easily wind driven by the Gulf Stream, Woods Hole Oceanographic Institution (WHOI) research specialist Mary Carman told The Times. It is not uncommon for man of war to appear in Island waters, but they usually die off in the winter months.
“People should definitely stay away from them. Up on the beach their sting can be powerful,” Carman said. Even when dead, people can still be stung by the six to eight foot long tentacles.
Updated to add comments from Mary Carman. — Ed.