EDGARTOWN (CBS) — Some Martha’s Vineyard beaches are closed to swimming until further notice due because of sightings of a “dangerous” jellyfish-like creature. Portuguese man o’ war are currently prevalent in the waters around the island, officials say.

The Edgartown Parks Department closed South Beach to swimming Thursday due to “large amounts” of the man o’war washing up on the beach.

“These jellyfish can be very dangerous and their sting can last for several hours,” the department said.

Elsewhere on the island, Long Point and Trustees properties on Chappaquiddick are closed to swimming because of the man o’war, The Martha’s Vineyard Times reports.

“Swimmers should pay close attention when in the water,” Edgartown officials cautioned.