It had previously served as the civilian survey vessel MV Edda Fonn in the Norwegian oil and gas industry.

The ship was built in 2003 by Myklebust Verft and delivered in May as MV Edda Fonn to Østensjø Rederi to serve as a survey vessel for work in the oil and gas industry.

[12] The New Zealand government had originally planned to purchase a newly built ship for these roles, with work on this project beginning in 2013.

[12][13] After NZ$148 million of funding for the project was diverted in 2017 to cover the unexpectedly high costs of upgrading the RNZN's two Anzac-class frigates it was decided to acquire a second-hand vessel instead.

The moonpool and remotely operated underwater vehicle hangar were remodelled, and specialist equipment including a multibeam echosounder, diving launch and recovery system, and davits were installed.

[30] During the same month the ship was used to carry 3.2 tonnes of cocaine to New Zealand after it was seized by the police during an operation in which the drugs were intercepted after they had been dropped in the Pacific Ocean ahead of being smuggled into Australia.

[31] In November 2023 it conducted undersea surveys and disposal of World War II bombs in Niue, Fiji, and Vanuatu.

[32] In 2024 the vessel carried out three deployments to the South West Pacific, including visits to Kermadec Islands, Samoa, Tokelau and Niue.

[33] On the evening of 5 October 2024, Manawanui ran aground around one nautical mile (1.9 km; 1.2 mi) off Siumu, on the south coast of Upolu island, Samoa, whilst carrying out survey work of a reef in rough seas and high winds.

[35] All 75 crew on board were evacuated by four of the vessel's life rafts and two rigid hull inflatable boats early on 6 October.

[41][42][37] At least 17 people were injured in the incident,[43] many from cuts and abrasions from walking on the reef, and three received hospital treatment, including one for a dislocated shoulder.

[45] The acting Samoan Prime Minister Tuala Iosefo Ponifasio said in a press statement, "The HMNZS Manawanui is not recoverable and has sunk into the ocean.

[52] Local Samoan residents expressed concerns about the impact of the ship's sinking on the maritime environment, and called for compensation and an independent inquiry.

[54] In early February 2025, Radio New Zealand reported that villagers in the Safata district had sought financial assistance from the Chinese Embassy in response to the Samoan government declining a request to provide affected communities with income and aid.

[55] According to Safata district spokesperson Tuai Pu'a Leota, the Samoan and New Zealand governments had not adequately consulted with local village leaders or provided financial compensation.

[56] On 12 February, the Samoan Government lifts a "precautionary zone" around the wreckage of the HMNZS Manawanui following testing by the Scientific Research Organisation of Samoa (SROS).

The MPAC despatched divers to recover ship debris, conduct water contamination tests and develop a plan to remove the remaining fuel.

MPAC chair Fui Mau Simanu reported that the sunken Manawanui and its anchor chain had caused substantial damage to the reef covering an area of 5,000 square metres (54,000 sq ft).

[60] On 19 October, the NZDF announced that work to mitigate pollution from the wreckage would be scaled down during the 2024 Commonwealth Heads of Government Meeting (CHOGM) scheduled for the following week.

[61] That same day, Prime Minister Mataʻafa confirmed that dive and coastal operations in the Safata region would be temporarily suspended for a week.

Committee chair Simanu said that fuel salvaging was expected to start in mid-November 2024 and last about 20 days depending on weather conditions.

[65] On 23 October, the third container was removed from the reef following four days of coordination between the NZDF, local contractor Ark Marine and the support of Samoan authorities.

In response, University of Waikato associate professor in biodiversity and ecology Nick Ling expressed concern about the pace of the removal and the monitoring of oil leaks.

[69] On 18 November, Deputy Chief of the Navy Andrew Brown confirmed that work to remove the fuel and other contaminants from the HMNZS Manawanui is expected to commence in December 2024.

[70] On 25 November, the NZDF dispatched a barge carrying salvage crew and equipment to assist in removing oil and other pollutants from the southern coast of Upola.

[71] On 24 December, the NZDF confirmed that the salvage barge had arrived off the south-west coast of Upolu island and would commence fuel extraction soon.

[73] On 10 October the New Zealand Defence Minister Judith Collins condemned these activities, labelling them a "deeply concerning misogynistic narrative".