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Mass. beaches close waters due to Portuguese man o’ war sightings

Portuguese man o' war pack a powerful sting that is dangerous to swimmers.

A Portuguese man o' war. Julio Cortez/AP/File

Several Massachusetts beaches faced closures recently due to sightings of Portuguese man o’ war, venomous ocean organisms closely related to jellyfish.

A man-of-war, or man o’ war, sighting was reported in Yarmouth Monday, prompting the closure on the south side of town, according to the Yarmouth Division of Natural Resources.

Harding’s and Ridgevale beaches in Chatham were also closed multiple times over the last three days due to sightings of the ocean predator. Chatham officials asked beachgoers to abide by “No Swimming” postings around the area.

Sightings also closed Horseneck Beach Station Reservation in Westport on Sunday and earlier in the month. The beach reopened Monday following an assessment of the water.

Portuguese man o’ war pack a powerful sting that is dangerous to swimmers, both in and out of the water. While their venom is rarely lethal to people, it can leave whip-like welts on skin that last two to three days.


Man o’ war are often confused with jellyfish due to their long tentacles that can span up to 130 feet. However, it is actually a species of siphonophore, a different class of marine organisms.

Unlike jellyfish, man o’ war cannot swim, instead using wind and ocean currents to propel themselves forward. This contributes to the marine animals washing up onto beaches like Cape Cod.


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