A bronze whaler swimming close to shore sent swimmers scurrying from the surf at Papamoa Beach but a marine expert says the shark species does not usually present a threat to bathers.
On Tuesday, beachgoers had close encounters with the bronze whaler, with one person noticing it was just half a metre from where he was swimming.
Two hours later, a shark was seen splashing around in the shallows. It was unclear whether it was the same shark.
Department of Conservation marine scientist Clinton Duffy said bronze whalers were a common sight at Bay beaches in summer and people should not panic on sighting the species.
The only person to be killed by a bronze whaler in New Zealand was a spear fisherman at Te Kaha in 1976, Mr Duffy said.
"In summer time, they start coming in and the mothers will drop their pups in shallow water and hang around to feed.
"Normally they don't pose any risk to swimmers because they are a specialised fish eater."
Bronze whalers mostly fed on mullet, kingfish and eagle rays. Their teeth were not designed to feed on anything larger.
However, Mr Duffy warned if someone saw a shark and could not identify it, they should leave the water.
People should also avoid a shark if it was larger than 1.8m in size.
Aucklander Warrick Smith was boarding among the breakers when he saw people running from the water.
When he saw the shark's fin pass under his board he scrambled towards the shore with his family.
Craig Nicholls, 21, did not spot the shark until it was less than 1m from where he was body surfing. He said if he hadn't been close enough to distinguish the shark's sleek features, he would not have been too frightened.
Sightings of bronze whalers were common along the stretch of beach, especially over summer, Papamoa Surf Life Saving Club captain Shaun Smith said.
"It's a daily occurrence. The advice we give people is if they see a shark, to hop out of the water for their own safety."