Three small sharks have been spotted at Pauanui Beach in the Coromandel.
A surf lifesaving spokesperson told Newshub the lifeguards asked all swimmers to get out of the water.
Swimmers have been advised not to panic, as keeping out of the water for an hour from the last sighting is standard procedure.
The sighting comes after 19-year-old Kaelah Marlow died on January 7 after being pulled from the water by emergency services at Waihi Beach, in what's thought to be a shark attack.
Her death has been referred to the Coroner but initial indications are that she was bitten by a shark.
Felix Berghoefer from Kelly Tarltons told Newshub in December that most swimmers in New Zealand will be within 200 to 300 metres of a shark this summer.
"There are actually quite a lot of sharks in the water," he said. "They aren't bothered by people; they keep their distance."
Berghoefer said the most important thing to do if you run into a shark is to stay calm.
"Stay calm. That's really all it is because if you stay calm the shark is going to stay calm but if you get nervous, which is probably likely if you see a shark because that's most people's reactions, the shark is probably just going to get freaked out and swim away. I wouldn't expect a shark to become aggressive just because you get nervous."