The head of the police search and rescue team which failed to find missing woman Iraena Asher in 2004 says it's unlikely she went missing in the bush.

Senior Sergeant Mark Fergus told an inquest at Auckland Coroner's Court that it was more likely Ms Asher had drowned.

Ms Asher, 25, was last seen by Piha couple Zachary Dixon and Simone Ross naked under a street light near Piha beach, west of Auckland, about 1am on October 11, 2004.

They had followed her but after she disappeared from the street light's beam they couldn't see her, and after searching nearby assumed she'd gone on to the beach.

Ms Asher told a family she spent four hours with that night that she might head to the bush but Mr Fergus, who led the police search, says they couldn't find her on land after a five-day search.

"Between 2004 and now I think some evidence would have been found if she disappeared there," Snr Sgt Fergus told coroner Peter Ryan.

He said it was most likely she drowned.

Police inquiry head Detective Senior Sergeant John Sutton said Ms Asher's bipolar disorder produced manic episodes when she was stressed and not properly medicated.

On October 10 she went to Jesse Praggert's place in Piha along with two people who cannot be named.

Mr Praggert said she left for about 90 minutes at one stage and came back drenched up to her waist and dirty.

After a shower he said she danced around the room naked "like a stripper" for four hours.

During this time she consumed alcohol and some cannabis but no other drugs, the witnesses at the house said.

She left about 8pm and called police just before 9pm.

In two conversations she said she had felt pressured for sex, a claim her colleagues at the Piha house denied, and that she was feeling paranoid.

Police sent a taxi for her, a response they have since admitted was wrong, which never arrived.

Police changed their call centre procedures in the wake of Ms Asher's disappearance.

She then spent four hours with a Piha family, where her unusual actions included her words about spending the night in the bush, before leaving just before 1am.