A fourth day of searching in the Golden Bay region has failed to reveal any sign of missing Dutch tourist Ken Boogers, with police now holding grave fears for the 26-year-old's safety.
Mr Boogers was last seen on the Pillar Point track between Wharariki and Puponga on Saturday.
Bare-footed in a red t-shirt and beige shorts, he was reported missing by friends who are concerned he was unequipped for the conditions.
The Navy vessel HMRNZ Hawea joined today's search, covering the coastal area from Farewell Spit to south west of Wharariki Beach, while four ground teams were also involved.
"In the event that he has spent the last five nights in the open survivability is diminishing," Search coordinator Sergeant Michael Fitzsimons said.
There had been no confirmed sightings since midday Saturday, and no indication he had left the area.
Mr Boogers' parents had arrived in New Zealand.
The search was being independently reviewed to assess whether there were any other options left to cover, which will direct any decisions for further searching.