Diver's dad in the dark

Colin Smithies. Photo / Supplied

The diver who went missing for days sparking a major search had disappeared to kill himself, his father believes.

Gary Smithies said police told him they knew his son Colin was not missing at sea after the first day of searching.

There has been no explanation for the disappearance of publican-turned-economist Colin Smithies. A search was launched on Monday after he was reported missing on a diving trip at Titahi Bay, near Porirua. He turned up disoriented in Hawke's Bay on Wednesday and was charged with wasting police time before going into psychiatric care.

Smithies said detective senior sergeant Donna Howard told him police knew it was unlikely that his son was missing while diving.

Howard had also told him that there was another investigation that involved an aspect of his son's life but "she wasn't prepared to go into it". He said he did not know whether that was a factor leading to his son's disappearance.

He said he was told the resolution of that inquiry was "a month or two away".

"I asked her straight: 'What the f**k's going on?' But she said 'We won't be saying anything else at this stage'."

Smithies said he found the lack of knowledge difficult because the family still had no explanation for Colin's two-day walkabout.

Meanwhile, a 35-year-old Auckland man who hid out after sparking a missing person search has been charged with wasting police time.

Leon Sanders went missing on December 29. He was found safe on New Year's Eve.