A family swimming at Ruakaka beach left the water at top speed after they turned to see what had caused a loud splash and saw a shark "frolicking" nearby.
Emma Whyte said the splash made by the over 2-metre long shark they believed was a mako was loud enough to be heard above fairly rough surf yesterday at about 3.15pm.
Ms Whyte, who was in the water with two of her children and her sister-in-law, said the shark was about 100 metres from them, and was between the beach and the crab pots it may have been trying to dine on.
"We ran. It was freaky," she said.
"It really looked as if it was frolicking in the waves. The splash it made was huge and that was over the top of the sound of the waves."
Members of the family ran about 20 metres down the beach to where other groups were swimming to warn them to get out of the water.
Ms Whyte's husband and brother were sitting on the sand at the family's favourite swimming spot at the northern end of the beach and they also saw the shark as it leapt out of the water several times before disappearing.
They said the shark seemed to be paying close attention to the crab pots that had been put out offshore earlier by boat. The tide was on its way out at the time.
Ms Whyte said she had swum at the beach all her life and although she had heard bronze whalers, mako and other species were common, she had never seen one before.
Surf beaches such as Ruakaka or Waipu were closed two or three times a summer because of shark sightings.