A coroner has praised the efforts of an Auckland couple who risked their own lives to try to keep a drowning man afloat after a honeymoon snorkelling trip in the Cook Islands turned to tragedy.

However, coroner Chris Devenport said the captain of a Cooks Islands boat didn't appear to ask if prominent Christchurch businessman Graeme Leslie Parker, 37, suffered from any medical condition before the trip.

Mr Parker, the chief executive of Christchurch gaming trust Eureka, got into difficulty while snorkelling with his wife Huia in a lagoon at Aitutaki, October 26, 2009. They were on honeymoon, having got married just two days earlier.

Mr Parker suffered from diabetes and obesity.

The snorkelling trip had been organised through Bishop's Lagoon Cruise and the captain of the boat introduced himself as "Captain Awesome''.

Both Mr Parker and his wife got into difficulties when deciding to swim across a reef to reach the boat that had taken them near One Foot Island. While Mrs Patuwai-Parker was helped to the boat by an Italian couple, Auckland couple James Rennie and Hannah Goodburn went to Mr Parker's aid.

They held Mr Parker up above the water, but found they had drifted further away from the anchored boat.

Mr Parker had been responsive but suddenly his face went purple.

"James and I looked at each other and I suggested to James that he try to do mouth-to-mouth,'' Ms Goodburn said in her statement to the coroner.

Mr Rennie was able to blow get some air into Mr Parker's mouth, but it came out his nose again.

After an estimated five to seven minutes, the boat reached them and they got Mr Parker into it with some difficulty.

A German doctor and Mr Rennie performed CPR and they were later joined by a doctor from another boat but Mr Parker was pronounced dead within 10 minutes of arriving at Aitutaki's hospital.

Mr Devenport called the efforts of Mr Rennie and Ms Goodburn in risking their own lives to try to keep Mr Parker afloat "commendable''.

He found that Mr Parker died from drowning and likely cardiac arrhythmia.

He said standards in New Zealand for recreational snorkelling did not seem to apply in the Cook Islands and he reviewed Mr Parker's death in accordance with those standards.

While the captain had ascertained that the Parkers had not previously snorkelled he did not carry out a special briefing for them - or give a safety briefing.

"No steps appear to have been taken by the captain to ascertain if Mr Parker suffered from any medical condition, and no caution appears to have been given by the captain to Mr Parker before he commenced snorkelling,'' Mr Devenport said.

The boat did not have flotation devices and there was no evidence it had first aid or medical equipment on board.

The captain did not seem to have communicated to the snorkellers that he intended to move the boat away from the drop-off point and later when the problems developed, his speed of response was criticised.

"In Mr Parker's case, the impression given by Mr Rennie and Ms Goodburn was that the seriousness to Mr Parker's situation did not appear to have been fully appreciated by the captain, who in any event was retrieving other participants from the water and lifting the anchor,'' said Mr Devenport.

The captain was effectively filling the role of captain, crew, lookout and rescue person, because his two crew were on One Foot Island preparing lunch, "and he was unable to simultaneously fulfil all those roles adequately when the crisis occurred''.

The New Zealand snorkelling standard says there should be competent people on board appointed as rescue personnel.

Mr Devenport said that while he was unable to make recommendations to people outside New Zealand, it would be "of comfort to New Zealanders and others undertaking snorkelling activities in the Cook Islands'' if similar standards applicable in Australia and New Zealand were adopted there.

- © Fairfax NZ News