The police dive squad are searching the Whanganui River for the body of missing man Whetu Hansen, who is the possible victim of a homicide.
Mr Hansen, 48, was last seen on November 24 last year, and a homicide investigation was launched in December.
A 56-year-old man is currently appearing before the courts charged with his murder.
Detective Senior Sergeant Simon Harrison said the Navy were helping police with their search.
"We are unable to comment at this stage on what exactly we are looking for in the Whanganui River or why we have determined that a search of the river is necessary for the purpose of this investigation," he said.
Police were also seeking more assistance from the public in relation to Mr Hansen's disappearance.
The investigation team wanted to hear from anyone that saw a 1996 white Ford Courier ute in the Palmerston North or Whanganui area on Wednesday December 4, 2013, he said.
"I would encourage anyone that has any information about this vehicle or the death of Whetu Hansen to contact their local police station or Detective Dave Wilson of the investigation team on 06 213 9595."
Information can also be provided anonymously to the organisation Crimestoppers on 0800 555 111.