THIS is the rare and potentially dangerous jellyfish spotted locally which swimmers are being urged to avoid.

They may resemble a plastic bag, but the exotic Portuguese man-of-war packs a powerful punch and they are being blown in to the Dorset coast.

These floating colonies have a powerful sting on their long tentacles, which hang from a balloon-like float, which keeps them at the surface of the sea.

A live creature has been found in Kimmeridge Bay - the third to be reported along the county's coast over recent days.

"We haven't seen any of these in Dorset for several years and you wouldn't want to meet one while swimming," said Julie Hatcher, Dorset Wildlife Trust marine warden.

"They are very rare here, but every few years we see some blown across the ocean.

"The one we have here is six inches long, but they can be bigger.

"There could still be more about, so we would advise people not to touch them but to let us know," she said.

The creature can be seen in the Marine Centre at Kimmeridge Bay, but you would normally have to travel to warmer tropical and subtropical seas to encounter one.

They usually live in the waters of the Florida Keys and Atlantic coast, the Gulf Stream, Gulf of Mexico, Indian Ocean and Caribbean.

Any further sightings should be reported to Dorset Wildlife Trust on 01929 481044.