Surfers have been warned to avoid Matakana Island in the coming weeks after a great white shark "leaped out" at a teenager in the water.
Bay Boardriders president James Jacobs took to social media on Tuesday informing the community of a "near-miss shark attack" on Monday morning.
"A three metre-plus great white leaped out of the water in full-attack mode at a teenage boy who was pulling off the end of a wave while surfing yesterday."
Department of Conservation marine expert Clinton Duffy said the encounter was "very concerning" with "potential for very serious or life-threatening injury".
He said it would be a "good idea" for surfers and kayak fishermen to avoid the area for several weeks.
Duffy said the surfer who caught the wave did not see the shark, and it was only witnessed by someone at the back of the break.
"I only spoke to the person that witnessed it, but it was all over in about a second. The shark launched out of the water where the boy should have been.
"He was very concerned. It was clearly a near miss."
Duffy said the shark was "larger than most" that had been reported in the area recently.
He reminded water users that great white sharks were an endangered, protected species and it was illegal to harm them.
Shark scientist Dr Riley Elliott said the incident sounded "pretty scary" as the shark was "seemingly showing interest" in the surfer.
"This is concerning because it's a capable predator [meeting] a human. We don't want those two interacting in that manner."
He said North Island harbours were one of only three places in the world identified as hotspots for great white nursery grounds.
"And for the animals that is very important. But unfortunately, this overlaps with one of our biggest holiday and surfing destinations in the country."
Elliot appealed to DoC for permission to launch a project investigating great white shark distribution in the northeast of the country in November 2020.
He said it was important to understand shark numbers and activity, which could be done through tagging and tracking.
"It is incredibly frustrating that I can't empower people who live and recreate in this area with an understanding of where the sharks are and what they are doing there. Because if we track these sharks we know exactly where they are in real time."
This work was important so swimmers, surfers and fishermen could make decisions about how to use the ocean, he said.
Kaelah Marlow, 19, of Hamilton, died after a shark attack off the beach at Bowentown on January 7 last year.
In December, DoC issued a warning for water users, saying there had been a rise in great white shark sightings in Tauranga Harbour, including Bowentown, and along the area's ocean coastline.
Two dead great whites washed up on Bowentown Beach and local fishermen reported brushes with the endangered species.
Elliot feared another incident could take place before he received a decision about his permit.
"It has already taken a year and a half, but it should take 20 working days. There has been a human fatality in that time."
DoC marine science adviser Karen Middlemiss said it continued to "work through" Elliott's permit application and was consulting with iwi - a "core and important part" of the application process.
She said although there may have been an increase in great white sightings in and around Tauranga Harbour in recent years, it was "unlikely" a tracking study would identify any places the sharks like to frequent that aren't already known to locals.
House of Surf business owner Lauren Ringer said the incident highlighted the importance of taking extra steps to be careful when surfing at Matakana Island - including avoiding going out at night and always taking a buddy.
Ringer, originally from Australia, said although it sounded "pretty traumatic", it did not put her off surfing there.
"There is an innate desire to be in the ocean - and I can't really change that.
"But does it make you more mindful and maybe you make different choices? Totally."
The surf coach said she had seen sharks twice in recent weeks while taking lessons along the coast, with one nearly half a metre.
After both encounters she immediately brought students into shore.