Auckland swimmers are being warned to take care as several beaches experience jellyfish blooms.
A jellyfish bloom is a sharp rise in jellyfish numbers within a short period of time.
Auckland Regional Public Health said warm water is attracting the jellyfish towards shore.
Their stings can cause some beachgoers to break out in a rash known as "sea-bather's eruption".
The health authority said children and those with allergies may get more severe reactions and become unwell for several days.
Bluebottle jellyfish - which produce a nasty sting - have also been spotted around the coast, with people being told to stay out of the water if these jellyfish are present.