A sperm whale is understood to have flipped a boat at Goose Bay, claiming the lives of five photographers near Kaikōura.

The fatal accident happened about 10am on Saturday when a whale breached directly underneath the boat, capsizing the charter vessel, the Herald has been told.

Six people were thrown overboard, including the skipper. Five others were trapped underneath the upturned hull and didn't survive.

No one who was on the boat at the time of the tragedy could be reached for comment.

According to their website, the 10 keen photographers from the Nature Photography Society had planned the three-day field trip to Kaikōura for months.

Everyone made their way to the popular seaside village on Friday September 9 with a desire to photograph the landscapes, seascapes and birdlife of Kaikōura.

The trip coincided with the Kaikōura 48-hour photography exhibition, and they could enter the competition with photos they had taken in August.

One of the highlights of the weekend was a three-hour "birding trip" with Fish Kaikōura Charters at a cost of $80 per head.

The three-hour charter would take the group out on the water to capture photos of the snow-capped Kaikōura landscape in the background and the birdlife along the coast.

Whale watching wasn't on the agenda.

Safety briefing held, life-jackets were worn

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Saturday was a perfect day boating with sunny skies and the promise of a great day for capturing stunning photos.

The Herald understands from a close source there was a safety briefing and the group were wearing life jackets - a standard procedure for fishing charters.

The group set out at 9am in the 8.5m aluminium boat, leaving South Bay at Kaikōura and heading down the coastline to Goose Bay near the well-known twin road tunnels on State Highway 1.

The normally rough seas were unusually flat and calm, almost glassy, with no real swell and not a breath of wind.

After an hour the charter headed north towards Barneys Rock, a popular spot for photographers and tourists.

The rescue underway at Goose Bay. Photo / Supplied

Whale came up directly beneath the boat

Barneys Rock is less than 100m from shore and just north of the double tunnels.

It is often covered with birds and is known for seals.

As the charter boat motored slowly north it appears it was on the edge of the famous deep trench that is home to whales.

The canyon quickly drops away to a depth of 500 metres and as far down as 3km.

The boat was about 500m from shore when, the Herald understands, a whale came up underneath the boat.

The skipper and passengers were tossed into the water.

A Goose Bay local says they saw the whale within "two or three hundred yards" from the boat.

Kevin Anderson said he saw a whale heading north, diving under the water near the vessel.

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

Survivors swam for the boat

The survivors would have been in the water fully clothed and in shock.

They would have hung onto the side of the upturned boat and pulled themselves up on top of the aluminium hull.

Six people sat on the boat waiting to be rescued, five passengers and the skipper. Five people were missing.

 

Scene from the helicopter of the capsized vessel. Photo / Supplied

Mayday call and rescue operation

As they waited to be rescued it appears that the boat drifted towards the shore on the incoming tide and gentle swells.

A mayday call was overheard on maritime radio and Kaikōura helicopter pilot Daniel Stevenson flew to the scene in four minutes.

Kevin and Erin Anderson were eyewitnesses to the tragic boating accident at Goose Bay on Saturday morning, and said they saw a whale in close proximity to the upturned vessel. Photo / Tim Cuff

A nearby boat picked up the five passengers off the capsized vessel and took them to South Bay, the Kaikōura marina less than 20 minutes away.

The Kaikōura Coastguard was dispatched and attempts were made to get under the boat to try and save those still in the water.

Stevenson picked up a diver from Kaikoura and flew him to the scene. He jumped from the helicopter into the water.

He managed to get under the upturned boat but could not save those trapped below.

Four of the five victims have so far been identified.

Christchurch's Peter Charles Hockley is believed to have been in the vessel's cabin alongside the four other victims when the boat capsized. His daughter said he was an avid photographer and an "amazing dad".

Diana Stewart, 68, was a receptionist at Dental Place NZ, which wrote on Facebook that they were "deeply saddened" to hear her death.

"Ever kind and caring, Diana was an expert photographer with a passion for nature, and will be sadly missed by all who knew her. Our deepest condolences to her family."

Susan Cade was a much-loved member of the Wellington community, remembered by friends as a keen kayaker, photographer and dancer.

Lower Hutt woman Susan Cade died in the Kaikōura boat accident. She has been remembered for her love of dance, photography and kayaking by friends. Photo / Supplied

Cade's close friend Cathye Haddock also died when the 8.5m charter vessel capsized.

Haddock, who worked at the Ministry of Education and loved the outdoors, had recently joined the photography society, her husband Peter Simpson said.

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

The couple who operate the fishing charter business said it was an unprecedented tragedy.

Fish Kaikōura owners Mark and Sharlene Ealam said their thoughts and prayers were with the families and friends of the dead.

They said they were in shock and requested privacy during what they described as a "terrible time".

Three investigations under way

The Transport Accident Investigation Commission is investigating, in conjunction with Maritime New Zealand and the police.

The commission has started to contact witnesses and wants to hear from anyone who saw or recorded what happened.