The HMNZS Manawanui capsized and sank on Sunday morning after hitting a reef off the southern coast of Samoa. Photo: Profile Boats / supplied
The Navy ship HMNZS Manawanui has sunk off the coast of Samoa after running aground on a reef.
The 75 passengers and crew were evacuated into life rafts after the incident on Saturday night - a move that authorities say likely prevented loss of life.
But what caused the crash, what's next and how much will the ship cost to replace?
Here's what we know.
The sinking
The nearly 85-metre HMNZS Manawanui was on its third deployment to the southwest Pacific this year after leaving Auckland in late September. The ship is a specialist dive and hydrographic vessel that is used to carry out a range of support, salvage and survey tasks.
Crew on board had been conducting a reef survey before the ship ran aground about 1 nautical mile off the south coast of Upolu, Samoa's second-largest but most populated island, which includes the capital Apia.
Unsuccessful attempts were made to get the ship off the reef before it began to list (lean to one side).
The passengers and crew were evacuated using four life rafts and two rigid hull inflatable boats, Chief of Navy Rear Admiral Garin Golding said.
Samoa Fire and Emergency Services Authority staff help the survivors ashore. Photo: Samoa Fire and Emergency Services Authority
Due to the "extremely challenging" conditions, it took the first survivors five hours to get to shore. An Air Force P-8A Poseidon was deployed to assist.
One of the small boats "flipped on the reef" during the rescue attempt and those who were on board walked to land, Golding said.
Samoa fire commissioner Tanuvasa Petone said three people who were on board needed hospital treatment.
"They ... have some minor injuries, and so we treated them at the site and transferred to them to the hospital."
Golding said one person had a dislocated shoulder, while another had injured their back.
After all the survivors were ashore, the ship caught fire, capsized and sank. It was underwater by 9am on Sunday.
Returning the crew
The Defence Force has sent planes to Samoa to bring the crew home.
A Super Hercules C-130J took off from Whenuapai airbase about 7pm Sunday for its first international deployment, arriving in Apia around midnight, carrying medical and welfare personnel, a dive team, and light clean-up equipment.
It was set to return to Auckland on Monday night with 72 of the crew and passengers from the ship, while the remaining three would return to New Zealand on Tuesday on a commercial flight.
A second C-130H Hercules aircraft also took freight to Samoa on Monday morning, returning the same day.
Environmental concerns
The Defence Force is also working with local authorities to assess the environmental impacts of the ship hitting the reef.
Residents have been reporting an oil-like substance in the water around the wreck, and rubbish floating everywhere, and local conservationists say they want the wreck removed to preserve the delicate ecosystem.
The reef is home to an array of fish, rays, and coral - and is famous for its large population of sea turtles. It is an important food source for the island, and also serves as a tourist attraction.
Rear Admiral Golding confirmed about 950 tonnes of diesel fuel were onboard the ship when it sank, but the Defence Force has confirmed this was Automotive Gas Oil, a light-oil diesel commonly used by commercial and military vessels.
University of Waikato coastal science Professor Chris Battershill - who has dived in the area before and was involved in the cleanup from the Rena wreck and subsequent oil spill, said automotive gas oil was a lighter oil and the more toxic hydrocarbons would evaporate. The longer-chain hydrocarbons that were left would be less damaging to the environment, but could also be more difficult to clean up.
The Manawanui was also carrying "several marine standard chemicals" on board, including cleaning products and emissions control products like marine urea solution, the NZDF confirmed.
"There were no hazardous chemicals onboard beyond those that would be carried by most commercial ships," a spokesperson said.
Rear Admiral Golding said "our partners and friends" - countries including Australia and the United Kingdom - had offered aid to the Defence Force to salvage the ship.
Fact-finding mission and maintenance
Defence Minister Judith Collins said the reason for the grounding was unknown and it was too early to speculate. She said there would likely be a Court of Inquiry to establish exactly what had happened.
The Defence Force on Monday confirmed the Court of Inquiry was being set up, with Rear Admiral Golding confirming on Tuesday morning the team and terms of reference were close to being finalised.
The Court of Inquiry is an investigative body rather than a court of law, and the Defence Force announced on Monday one was being set up to investigate the sinking.
It aims for "expeditious" fact-finding, and while it can lay blame, it cannot hand down punishments and other courts cannot use its findings as evidence.
Rear Admiral Golding said some parts of the inquiry would be public, but others - including where commercially sensitive information was involved - would remain confidential.
The Manawanui, pictured in Auckland in 2023. Photo: RNZ / Ella Stewart
He has also confirmed the ship had been "in a maintenance period" before it was deployed.
Sources had suggested to RNZ concerns had been raised about potential oil leakage from the ship's engine before it left, but he said trials were conducted after the maintenance period and the ship "was determined safe to deploy".
Costs and insurance
NZDF has confirmed the Manawanui had "the equivalent of third-party insurance".
"The ship itself is not covered by insurance, as historically RNZN vessels are not insured due to the prohibitive cost. Even if purchased, policies are heavily limited by exclusions and conditions that apply to many activities our Navy operate in, such as shallow waters and cyclone responses."
The insurance available could help cover at least some of the costs of the cleanup and environmental response, though the total cost of salvaging, and the Court of Inquiry, remains unknown.
Replacing the HMNZS Manawanui itself is another expense.
The government in 2018 said it would cost $103m to buy and refit the ship, which had previously been a Norwegian commercial vessel. It was completed in 2019. Adjusting for inflation, that would be about $129 million today, according to the Reserve Bank.
The former defence minister who signed off on the commissioning of the ship, Ron Mark, told Morning Report the refit had been an innovative way of meeting the Defence Force's needs, and had become the "swiss army knife" of the navy.
A survey ship had been needed after the HMNZS Resolution was decommissioned in 2012, and a dive ship after the decommissioning of the previous HMNZS Manawanui in early 2018. Until it sank, the Manawanui was able to survey harbours and approaches to ensure they were safe for larger ships. It was able to perform salvage operations, and remove explosives left in the Pacific from wartime.