A man is thought to have fallen from a bulk carrier off the Otago coast.
The Chinese national was last seen at 8am yesterday when he finished his shift on the UK-flagged Berge Rishiri ship, but failed to report for duty that afternoon.
A thorough search of the vessel was carried out and it retraced its journey, searching for any signs of the man in the water.
The Otago rescue helicopter and a nearby vessel also scoured the coastline, but the search has been put on hold.
Maritime New Zealand believed there was little chance the person could have survived in the water.
A review was being carried out to assess whether a further search would be successful.
The Maritime Union said the loss of the crew member was very concerning and more common than many people realised.
The Union's national secretary, Craig Harrison, said New Zealand needed to do more to protect the welfare of international crews in our waters.
Harrison said he wanted to see Maritime New Zealand investigate whether the crew were having adequate rest breaks, and that they were not required to secure any cargo while underway.
He said it was common practice with some New Zealand stevedores with low standards to have overseas seafarers lash cargo when the vessel is underway, rather than shore based stevedores doing the work in port.
The sea time the crew member had been working for should also be investigated, he said.
"We would like to know how long the seafarer had been at sea and on duty and have assurances they were not kept on the vessel longer than their contracted period, as we have seen huge mental health issues with Seafarers basically kept captive on vessels for months and sometimes years," Harrison said.
"These crew members are in New Zealand waters, their work is essential for New Zealand, and in our view their rights and welfare are often overlooked."
Harrison said New Zealand authorities must do a full investigation into the incident.