A dive company owner has described a group apparently fishing inside a marine reserve as a "blatant and reckless raiding party".
Video posted on social media appears to show the men at the Poor Knights islands off the Tūtūkākā Coast in Northland.
The area has been protected for decades and is known as one of the world's best dive spots.
A series of expletive-laden videos were uploaded as stories on Instagram.
"You fullas caught any f**king fish yet or what?" said the man filming.
"Ah, got a small feed, got a few in there and then just doing a bit of a clean up in here," said another fisher.
"A little bit of f**king marine life. Stop picking on the marine life aye. F**k, leave them alone."
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But the video depicted more than just harmless fishing banter.
According to those who know the area, the surrounding rocky islands are unmistakably the Poor Knights - a pristine and unique environment that has been a marine reserve where all fishing is banned since 1998.
"I felt sick to the stomach, it was really blatant, it's a total disregard," Dive! Tutukaka owner Kate Malcolm told Newshub. "It's disrespectful. It's like a raiding party."
Malcolm and her crew are at the Knights every day taking locals and tourists diving in the lush kelp forests which are home to an array of unique fish species.
"I had to look twice. I could not believe they would do that in broad daylight and put it up on their socials."
"They are flipping the bird to everyone. Everyone who sees that place as a special taonga and a turangawaewae. They are flipping the bird to the iwi, to the locals here. This is our area."
The Poor Knights are rated as being in the top 10 places to dive in the world.
The marine reserve extends 800 metres out from the two main islands and covers all nearby rocks and reefs, including the Pinnacles and Sugar Loaf.
Kahawai Point near Punawai Bay appears to be in the video - in the middle of the marine reserve. It's where Malcolm says a kingfish is reeled in.
"It was easy to recognise that that kingfish was caught at Punawai Bay simply because of the background, the typography of the island," she said.
Northland Dive founder Julia Riddle told Newshub she's "100 percent sure" it's the Poor Knights and the posts left her feeling "sick".
"I'm still in total disbelief that someone would blatantly fish at the Poor Knights Islands and have the balls to boast about their catch on social media," she said.
"You can clearly see they're well within the marine reserve boundary and this would have been displayed on their GPS unit, so they have absolutely no excuse."
Chris Scott, from the recreational fishing group Legasea, is appalled.
"This isn't a reflection of recreational fishers. This is poaching and the two are completely different," he said.
"You look at these guys, they're out there with a cavalier attitude, they're pulling in semi-tame fish from a marine reserve. This is highly illegal."
The Department of Conservation told Newshub it's been "made aware of illegal fishing at the Poor Knights Marine Reserve" and it's actively investigating the case with support from Fisheries New Zealand.
The videos were posted on Instagram by a Northland fishing and hunting enthusiast who has 33,000 followers. He's since deleted the videos.
Given the blatant nature of the alleged offending, Malcolm expects a swift response from authorities and more than just a warning.
"There is no excuse for what they've done. If the government departments involved in this cannot prosecute on such a base case as this, I would be really disappointed. They need to throw the book at them."
Penalties for fishing in marine reserves range from being fined to having your boat seized, or even jail.
Newshub sought comment from the man who posted the videos - he's yet to respond.
