Gary Donison, who was holidaying on the island with his wife Leslie, died after surfacing from a dive with tour operator Bubbles Below.
Police confirmed the Coroner had ruled the cause of death was drowning with aspiration causing asphyxia and eventual cardiac arrest.
The 60-year-old company director is suspected to have suffered blocked blood flow to part of the lung, contributing to the drowning.
Police spokesperson Trevor Pitt said the coroner had released the body of the deceased, so Leslie could fly him home to Edmonton in Canada.
But Bubbles Below owner Onu Hewett disputed the ruling, and maintained Gary died of natural causes (cardiac arrest) and not from drowning.
Hewett said the deceased’s dive watch recorded 32 minutes diving and a four-minute safety stop before he ascended, which he said was longer and safer than usual.
Upon surfacing, Gary inflated his own buoyancy compensator, and was on the surface for several minutes before anyone noticed he was unresponsive, Hewett added.
“He was still wearing his mask. Readings from Gary’s watch were normal. He still had 60 bar of air left when he surfaced, which is a quarter of a tank, or plenty of air.”
Hewett said Bubbles Below had been operating for 15 years and they had never experienced such a tragic loss. “We are committed to safety; we check equipment and brief our guests before every dive. Gary had logged more than 400+ dives, so he was a very experienced diver and familiar with all safety procedures. He was also using his own equipment.”
The family of the deceased had earlier thanked Hewett for supporting Leslie Donison throughout the ordeal. He had flown to Rarotonga with Leslie and the body, and remained with her until her friends arrived.
Gary’s sister Pamela Donison said: “We are all heartbroken and full of questions, but we have been comforted by knowing that Leslie is being helped by the open hearts of Cook Islanders.”
Leslie’s daughter Elizabeth, in a letter to Cook Islands News, said: “I read your article on Gary out loud to my kids and my brother and his family and it brought tears to our eyes and peace knowing my mom is being taken care of in this devastating time.”
Leslie also acknowledged the team at Bubbles Below and others who cared for her husband. “They did everything they could to revive him, right up until they got to shore and the doctors took over,” she said.
Leslie said diving in Aitutaki was a dream come true for her husband. On the morning of Gary’s accident, he told Leslie that he wanted to come back to the Cook Islands.
Gary was thrilled by the friendliness and warmth of Cook Islanders, she said.