Surfers and swimmers are reporting being stung by hordes of small jellyfish at an Auckland's Piha beach.
A surfer who hit the west coast waves yesterday evening told the Herald "stacks" of tiny jellyfish floated around him in the water and he got stung all over his arms, legs and neck.
"The worst sting was right on my lip," he said.
"Pretty much every surfer in the water was complaining about getting stung, particularly those in spring suits. A shorty [wetsuit] definitely wasn't a good idea last night."
The Auckland man said he would usually have stayed in the water until the sun went down, but he decided to call it a night after his lip was sting.
"I got off lucky. Another guy showed me a massive sting on his leg that he got the night before. Hopefully, they don't hang around too much longer."
Niwa emeritus researcher and jellyfish expert Dennis Gordon said warm water can cause a bloom of plant plankton, which boosts jellyfish numbers.
Gordon had heard that "massive amounts" of jellyfish had washed up on west coast beaches from Dargaville to Wellington at the end of last year.
The warmer water could also bring about "sea sparkle", Gordon said, which was a tiny planktonic organism that was transparent in the light.
"It all lights up and sparkles in the dark, it's quite pretty."
The Auckland Council's website says most jellyfish stings in New Zealand are not serious if promptly treated but recommends swimming elsewhere if jellyfish are spotted.
How to treat a jellyfish sting:
&blob; Wash the affected area with fresh or saltwater.
&blob; Remove any tentacles or stings attached to the skin – but do not touch them with bare hands.
&blob; Place the affected area in warm water (45C).
&blob; Do not apply vinegar, methylated spirits or alcohol, as these will make the sting more painful.
&blob; Calamine lotion, antihistamines and steroid creams may be helpful.
&blob; If the reaction to the sting is severe or the symptoms worsen, see a doctor. If the person has reduced consciousness or difficulty breathing, call 111 and ask for an ambulance.
- Source: Auckland Council