A lone bunch of flowers sits among the rocks at Goose Bay in Kaikōura as the area mourns those lost in a tragic boating accident that claimed five lives.

At South Bay, where the Coastguard is based, the flag hangs at half-mast and locals spoken to by the Herald expressed shock, grief and sadness.

One man who witnessed the rescue operation described it as a "terrible tragedy". Another said people in Kaikōura were feeling "pretty numb".

The skipper's wife expressed her sorrow for the victims' grieving families, describing the incident as an "unprecedented tragedy".

Shortly after 10am on Saturday, an 8.5m Fish Kaikōura charter boat, with 11 people on board capsized in "perfect, flat" conditions.

Marlborough police acting response manager detective sergeant Michael Whitty said five people were located deceased. The remaining six were assessed by medical personnel, and one was transferred to Christchurch Hospital, where they remained in a stable condition.

"To lose five lives is devastating and their loss will be felt widely across the country."

The vessel had been recovered and several investigations were now underway to ascertain how the accident occurred.

Formal identification of the victims was continuing and police were unable to confirm their identities yet.

"Police's focus remains on supporting everyone involved, including the victims and their families, their local communities, and emergency services personnel."

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Photo from a helicopter circling the upturned vessel in Goose Bay with one person seen on the hull. Photo / Supplied

The widower of a woman who died in the tragedy said he felt like he had been run over by a truck.

Peter Simpson's wife Cathye Haddock, who worked at the Ministry of Education and loved the outdoors, had recently joined the photography society and went on the birdwatching trip with a friend.

"When I saw the news report something had gone wrong, I contacted police and came to know," he told Discovery's AM.

Cathye was a real people person, Simpson said.

"She managed to fit everybody in her world.

"I have been in contact with Cathye's friend's family who was on the boat and also died.

"There is lot of speculation in the media and I don't know what happened. I am happy with police's process."

Simpson said he hadn't heard from the charter boat operators.

The daughter of a Christchurch man killed in the incident said he was an avid photographer and an "amazing dad".

She told Stuff her father, Peter Charles Hockley, is believed to have been in the vessel's cabin alongside the four other victims when the accident happened. The family learned of his death late Saturday afternoon.

"We don't even know who else is dead and who else survived. We just know that dad was one of the ones in the cabin."

Otematata Residents' Association chairman Steve Dalley told the Herald Hockley was a well-thought-of man who would be dearly missed.

The late photographer owned a holiday home in the area and enjoyed the wildlife and photo opportunities it offered.

Hockley took the photos for a calendar each year the association used as a part of a fundraiser to help pay for the upkeep of the Otematata wetlands which Hockley was very fond of. His photographs had a "cult following", Dalley said.

"He was a very kind, humble man, generous to our community and very well thought of."

Stuff also identified a second victim, with the Lower Hutt woman's husband saying he is distraught at news of her death.

A Goose Bay local told the Herald he spotted a whale within "two or three hundred yards" (182-274m) of the accident site on Saturday.

Kevin Anderson said while the rescue was still unfolding he saw a whale heading north, diving under the water in the vicinity of the vessel.

The retiree said there was nothing else near the vessel at the time and the sea was dead calm.

Kevin and Erin Anderson were eyewitnesses to the rescue of the tragic boating accident at Goose Bay on Saturday morning. Photo / Tim Cuff

Anderson said he had never seen anything like it in the 20 years he'd lived in the area.

"We were watching the television and because we had the glare, I had the blinds down and when we'd finished watching we put the blinds up and there's this boat upside down just out here. And there were five or six people clinging to the top of it."

Anderson said he saw a white boat heading towards the upturned vessel and picking up all but one of the people.

The Coastguard then arrived and the remaining man on the boat indicated with his hands that there were four or five people still under the boat.

Anderson spotted the whale shortly after the Coastguard arrived.

He said they only saw whales near their home "once or twice" a year, which normally did not go close to boats.

"Terrible, terrible, terrible tragedy that's just out of the blue, there's nothing you can do."

Police have not confirmed whether a whale caused the boat to flip, saying only that the vessel collided with "something".

However, Kaikōura's mayor Craig Mackle said on Saturday he believed the boat had hit a whale.

Whales were resident and had been seen in the area, Mackle said, and sea conditions at the time were "perfect, flat".

He said it was a tragic event that affected many lives, not least of all family and loved ones.

"Our heartfelt sorrow and condolences to you all."

'We're grieving with you and we're so sorry'

Fish Kaikōura Charters owner Sharlene Ealam, who is married to the boat's skipper, told 1News the incident "was an unprecedented tragedy".

"Our thoughts and our prayers are with the families and the friends of the deceased," she said.

"And I just wanted to say thank you so much to the first responders and for all of the support and love that we've all received.

"We're grieving with you and we're so sorry," Ealam said.

Ealam said she couldn't comment on what caused the boat to capsize, but confirmed the company would co-operate fully with the investigation.

A bouquet of flowers placed in the beach at Goose Bay, the day after the tragic accident that claimed the lives of five passengers on a charter boat. Photo / Tim Cuff

Yesterday, the photography society whose members were on the boat also spoke of their "tragic loss".

"The Nature Photography Society of New Zealand is saddened by the tragic loss at sea in Kaikōura during a trip by society members that took the lives of five of our members," the group posted on Facebook.

"Our thoughts are with the families of those members of the society who have lost their lives."

Dr Murray Cave, chair of the Nature Photography Society of NZ Honours Board, said Saturday's charter was the first sea trip for members since Covid-19.

Nature photographer, Gary Speer, said he went on a birdwatching trip off the Kaikoura coast several years ago as part of a Photography New Zealand conference.

Speer said the boat that went out yesterday would have been moving along slowly with someone throwing fish out the back to attract birds.

"If they had hit a log moving slowly it would have caused a bit of a slump but not tipped the boat over. A whale coming up would have," he said.

Appeal for witnesses

Meanwhile, the Transport Accident Investigation Commission (TAIC) is appealing for witnesses who saw the accident unfold.

Chief investigator Naveen Kozhuppakalam wants to hear from anyone who saw or recorded what happened – before, during or after the incident.

"The Commission investigation will run alongside investigations from other agencies. Two investigators are assigned to secure evidence, talk to witnesses, examine any electronic evidence available and look at the circumstances of the incident."

Richard Hill from Cods and Crays fish and chip shop told RNZ he had worked with the skipper on the boat before.

"He's a very safe man, there's no way he'd take any risks.

''So there's just got to be something, sort of a freak of nature, I would have thought. A very sad day for Kaikōura really, just a shock," Hill said.

Hill visited Goose Bay yesterday to pay his respects.

A man stands near the bouquet of flowers placed in the beach at Goose Bay. Photo / Tim Cuff

He told the Herald people in Kaikōura were feeling "pretty numb" because they had been through "so much" already.

"This is another thing for Kaikōura that we don't need really, it's terrible, poor families."

Tracy Phillips, Maritime NZ principal investigator, said the organisation had sent two investigators from Christchurch to Kaikōura.

"Any investigation activity will commence only after rescue/recovery operations have concluded. We'll be conducting a thorough investigation under the Health and Safety at Work Act and the Maritime Transport Act and we'll do everything we can to support NZ police in their investigation."