More details about the fatal capsizing of a boat carrying bird watchers off the coast of Kaikōura in 2022 will be revealed in a transport investigation report on Thursday.
Two hours into the i-Catcher excursion in September 2022, it capsized off Goose Bay, killing five of the 11 passengers on board when they became trapped under the flipped vessel and were exposed to petrol fumes.
Maritime New Zealand in 2023 ruled the likely cause of the capsize was a whale hitting the vessel, and decided not to take prosecution against any people, organisations or businesses.
The Transport Accident Investigation Commission's final report is due to be released on Thursday afternoon.
It had already produced a preliminary report, finding a fuel leak contributed to the five deaths.
The report found petrol almost certainly leaked from holes in the 8-metre aluminium boat's fuel system, and the five people who died all showed symptoms of petrol exposure, consistent with inhalation and absorption of petrol fumes.
That can lead to "confusion, loss of consciousness and sudden death", it said.
The i-Catcher had been inspected by five different marine surveyors during its 13 years of service and not one picked up any problems, TAIC said.
It called on Maritime New Zealand to improve its boat survey system, which did not require a vessel's entire fuel system to be inspected.
The final report is expected to make more recommendations, and detail the direct cause of the capsizing.
Those who died were Catherine Margaret Haddock, 65, and Susan Jane Cade, 63, of Lower Hutt; and Diana Ruby Stewart, 68, Peter Charles Hockley, 76, and Maureen Patricia Pierre, 75, all of Christchurch. All were members of the Nature Photography Society of New Zealand.
Their friends and families said they were devastated, and struggling to come to terms with what had happened.
Mark and Sharlene Ealam, who ran Fish Kaikoura, the business the group had chartered the vessel through, said it was an "unprecedented tragedy".
"We're devastated. We're beyond words," Sharlene Ealam told RNZ.
Kaikōura Mayor Craig Mackle thanked everyone involved in the rescue and the recovery.
"Being able to bring everyone home is the best result in such a terrible circumstance," he said.
