A ‘virtually certain’ disaster averted: How a $1000 part nearly sank a Cook Strait ferry

Thursday, 7 May 2026

An 18-year-old rubber joint that had been in service for more than double its recommended lifespan ruptured on a Cook Strait ferry, causing a total blackout and leaving the ship drifting toward rocks.

A final report from the Transport Accident Investigation Commission (TAIC) into the incident on January 28, 2023, has found the Kaitaki was “virtually certain” to have suffered a very serious marine casualty if its anchors had not eventually held.

The vessel, carrying 784 passengers and 80 crew, was approximately one nautical mile off Sinclair Head when it lost all electrical and propulsive power in severe weather after the less-than-$1000 rubber component failed.

Mary Layton, who was onboard the ferry with her family, told Stuff at the time the vessel lost power suddenly. “It went dead silent,” she said. “I don’t know if we were floating around in circles or if they were in control.”

The ferry eventually limped back to Wellington that night. No injuries were reported, and everyone disembarked in the capital.

Investigators identified a safety-critical rubber expansion joint on the port auxiliary engine had ruptured, causing cooling water to rapidly drain from the system, the TAIC report stated.

This meant none of the four main engines could be restarted safely, leaving the ship without propulsion for about an hour.

The report found that while the ship’s operator, Interislander, had commissioned a risk analysis in 2007, it had not implemented the recommendation to replace such joints every two years.

The joint that failed was manufactured in 2005 and had been in service for five years.

“Had Interislander implemented the FMEA [Failure Mode and Effect Analysis] recommendations… it is very likely that the reliability of the REJs [rubber expansion joints] would have been assured and this incident would have been avoided,” the report stated.

‘Organised chaos’ after blackout

The TAIC report also criticised the “less structured” response from the ship’s engineering team, which one member described as “organised chaos”.

While the bridge team used a decision-support system, there was no evidence the engineers were familiar with or had implemented a similar system for machinery emergencies.

Further propulsion issues occurred as the ferry was escorted to Wellington by tugs, with a gearbox fault disabling one side of the vessel’s propulsion system near Wellington Heads.

The commission found Interislander’s management of risks associated with its ageing fleet had not kept pace with the increasing risks of operating in the “hostile” Cook Strait environment. It also highlighted that New Zealand lacks sufficient, readily available emergency towage and salvage capability to manage such foreseeable risks.

Recommendations were made for KiwiRail to review its emergency response planning and for Maritime New Zealand to prioritise a national maritime risk assessment and specific Cook Strait response plans.

In 2024, KiwiRail was fined $432,500 over the incident. The state owned enterprise took full responsibility for the blackout and gave a formal apology to the people impacted.

After the release of the final TAIC report, KiwiRail said it accepted the findings and welcomed the safety lessons offered.

“The incident was serious, and it prompted a comprehensive reassessment of how we manage and maintain our ferries, and how our crews are supported to respond quickly and safely in emergency situations through training, and regular exercises,” COO Duncan Roy said in a statement.

“The TAIC report reinforces the importance of component level maintenance, strong oversight and emergency preparedness. These principles are now embedded in how we manage our ships every day.”

An earlier version of this story stated the Kaitaki returned to Wellington 'the following day'. In fact, the ferry arrived back in Wellington that night. Amended: June 10, 2026, at 12.17pm.