A Wellington diver who made headlines when he mysteriously disappeared from Titahi Bay near Porirua gave an elaborate account of being abducted when he turned up some 300km away two days later.

Colin Smithies, 49, who has since lost his job as a senior economist with the Commerce Commission, walked into the Clive police station just south of Napier appearing dazed, Wellington District Court heard today.

He claimed to have been abducted by two men in a camper van who drugged him, dyed and cut his hair, shaved off his beard and sexually assaulted him, police prosecutor Sergeant Kevin Shaw told Judge Michael Behrens.

The next day, Smithies admitted the account was a lie.

He said he had tried to kill himself at Titahi Bay on January 10 so his partner would get an insurance payout.

But, Smithies confessed to police, he "had been unable to do so".

His partner was expecting him home about 8pm or 9pm from a diving outing and, when he did not return, she reported him missing.

An extensive sea, air and land search was sparked, costing an estimated $48,000, Mr Shaw told the court.

"It appeared he was deceased."

Standing in the dock at court this morning with head bowed, Smithies pleaded guilty through his lawyer Mike Antunovic to a charge of wasting police time.

Mr Shaw said a search of Smithies' computer showed that, in the weeks leading up to his disappearance, he had researched a number of ways to commit suicide plus possible methods of faking death and "how not to be found".

A receipt from the Warehouse showed he had recently bought items including hair dye, a tent and a non-stick fry pan.

After Smithies gave himself up to police, he was admitted to Wellington Hospital and remained there for about six weeks, Mr Antunovic told the judge.

The only medical report before the court said the father-of-three had clearly been suffering from significant clinical depression which had gone undetected for some time and had "taken a huge toll on him".

Mr Antunovic said his client's judgement had been seriously impaired.

"He was a very sick man who just simply lost it."

Looking back, Smithies acknowledged the "massive concern" he had caused his family and a large number of other people, and apologised.

He was now unemployed, seeking work, doing his best to recover and had no income or savings, Mr Antunovic said, telling the judge it would be "unduly harsh" to expect Smithies to pay full reparation for the search.

"He is nearly half a century old and has never put a foot wrong (before). Give him credit for that, sir," said Mr Antunovic.

Judge Behrens questioned Smithies motivation at the time of the offence, asking whether he was going to commit suicide or disappear. "Or did disappearing occur to you later, so the family could have the insurance? It might be a mixture of both."

The charge carries a maximum prison sentence of three months and/or a $2000 fine.

The judge imposed 300 hours of community work and ordered Smithies to pay $16,292 in reparation - about one third of the estimated cost of the search for him.