Coroner calls on MBIE to ban tankless diving device after accidental drowning

The day before he died, Shengwei Cao pulled out his new tankless diving device - a Wolach 919 - and tested it in the bathtub. By 11.30am on 5 March, 2023, the device, sometimes known as a hookah type system, was on the surface of the water off the coast of Mana Island, pumping air through an umbilical hose to Cao, who was diving below. About an hour later, a couple of boaties - alerted to a missing diver - pulled the 58-year-old's body from the water. He was declared dead onshore shortly after. In findings published on Wednesday, Coroner Amelia Steel ruled Cao's death an accidental drowning, with decompression complications a contributing factor. She recommended the Wolach 919 be banned from importation into the country and that the Ministry of Business, Innovation, and Employment (MBIE) launch an awareness campaign about such devices and a broader product review of risks and regulations. In her report, Steel said Cao, a painter from Lower Hutt, had been free diving for at least five years. He usually dived in shallow water close to the shore, and only when the weather was good, she said. Occasionally he would take pills for seasickness. Steel said Cao wasn't trained in scuba diving but hoped to learn and had discussed its differences with friends. An advertising image shows the Wolach 919. Supplied / Alibaba.com His online purchase of the Wolach 919 would enable him to dive deeper, she said, and he tested it in the bathtub on 4 March, 2023. The next day, the 58-year-old met up with six other friends and began diving off Mana Island around 11.30am. "Mr Cao was using the Wolach to free dive for the first time, while the other people were scuba diving." The Wolach was attached to a buoy. After several dives, Cao returned to the boat, complaining of seasickness and that the Wolach wasn't working. Steel said he needed help getting out of the water, which was unusual. But 10 minutes later, feeling better, he was back in the water. However, not long after, his friends requested to dive elsewhere and unable to get Cao's attention, they left him alone, Steel said. The skipper noted the 58-year-old's breathing bubbles on the surface as they went. When the skipper returned to the site, the rocky shore prevented him from approaching Cao. He headed back to the main group and alerted a passing boat to a missing diver. The boaties found Cao's body still attached to the buoy, in water about five metres deep, Steel said. The breathing tube and pump, which went from the surface of the water to Cao, were also attached to the buoy she said. "However, the mouthpiece attached to the breathing tube was to the side of Mr Cao's head, rather than in his mouth." A short time later on shore, Cao was declared dead by emergency services. Steel said a specialist from the Police National Dive Squad tested Cao's gear in a diving pool and among several findings noted the Wolach design left the diver with an inconsistent air supply, particularly at depths of around 4.5 to 5 metres. The specialist considered it to be a "dangerous system" leaving the diver in an unsafe position without immediately available air. The specialist found Cao's use of the Wolach, continuing to dive when unwell, and diving alone were all factors in his death, Steel said. 'Avoidable tragedy' Water Safety New Zealand said Cao's death was an avoidable tragedy that demonstrated the risks of diving alone. In 2025, more than 55 percent of the 79 drownings were people undertaking water activities by themselves, it said. Supplied / Water Safety New Zealand The organisation's kaihautū Māori Rob Hewitt said the coroner's findings read like a "tragic list of everything you must never do" when heading out underwater. "Diving in open water is absolutely not the place to try new equipment," he said. Hewitt told RNZ Cao's death hit home. Hewitt survived four days at sea in 2006 after a routine dive trip off Mana Island went wrong. "When I first ... saw the coroner's report and saw where it was, it sort of touched my heart and woke up a few thoughts of when I was lost out at sea." He said New Zealand men needed to understand they weren't bulletproof. "When the unexpected happens you need someone close to you who can immediately give you some help. Tragically this was not the case for Mr Cao." He said training, ensuring equipment was fit for purpose and diving with a buddy were critical. MBIE considering findings MBIE's manager of consumer services Simon Gallagher said the agency was considering the coroner's findings and recommendations and was committed to assessing any appropriate actions. He noted the Wolach 919 was not currently available for sale in the country, but recognised the importance of understanding and addressing potential risks with such tankless diving products.