Recently bluebottles, also known as Portuguese man o’ war, have been washing up on beaches on the Otago coast.
St Kilda Surf Life Saving Club captain Conall Duncan said they had been found at St Kilda, St Clair and Blackhead Beaches.
He was not sure they were all bluebottles, as it seemed as though there were also many types of small jellyfish.
The club advised people to keep away from them as some could sting, he said.
"We haven’t had major drama, but there was someone the other day who had a bit of irritation."
Most years "a few" of the creatures would wash up, but the the current influx was probably due to the warmer weather, he said.
Department of Conservation biodiversity manager Jim Fyfe said bluebottles appeared on the beach most summers.
"We have a connection in coastal Otago to the Tasman Sea through Foveaux Strait. This time of year in summer subtropical water is more likely to have these species."
Bluebottles were not jellyfish, but a colony of individual animals linked together, he said.
"They are just like a little hollow tube."
