Swimmers at popular Auckland beaches are being warned of the dangers of microscopic jellyfish.
The Auckland Regional Public Health Service says swimmers at Takapuna, Cheltenham, Narrow Neck and Read beaches have reported rashes likely to have been caused by their stings.
The jellyfish, which are too small to be seen, get caught inside togs and can cause a red, itchy and painful rash.
The health service says little is known about the jellyfish and until 2008 the rashes were thought to have been caused by sea lice.
Swimmers are also urged to take care at other Hauraki Gulf beaches.