A free diver hoping to reach greater depths tested a breathing unit in the bathtub before tackling coastal waters.
Shengwei Cao had recently bought the Wolach 919 surface-supplied breathing unit online because his friends had used one.
But, things didn’t go as smoothly in the sea as they did in his home and Cao drowned while diving off Mana Island, Porirua on March 5, 2023, the day after testing the unit in the bath.
Now a coroner has called for a ban on importing the recreational surface-supplied breathing device designed for “hookah” [tankless] diving after expert testing proved it required users to have the skills and knowledge required for scuba diving.
Coroner Amelia Steel is also recommending the Ministry of Business, Innovation and Employment [MBIE] assess broader Wolach 919 tankless systems to determine associated consumer risks, market presence and available regulatory options.
She also recommended MBIE initiate a public awareness campaign about using the Wolach 919 device and similar tankless systems by engaging with agencies including the Police National Dive Squad, WorkSafe New Zealand, Coastguard New Zealand, Maritime New Zealand and Water Safety New Zealand.
Cao, 58, had been a free diver for about six years but was not trained in scuba diving, his wife LiRong Kwang told police.
The Lower Hutt painter usually dived in shallow waters close to shore and only when the weather was good, she said.
He also suffered seasickness and took medication to ease the symptoms, the coroner noted.
Cao’s diving equipment, including a full-body wetsuit, harness, mask and snorkel, dive weight belt, dive vests with extra weights and dive bag included equipment he had bought and made himself.
On March 5, 2023, Cao left home between 7 and 8am.
He met a friend, Chen Koo, at the Mana Boat Club, launched Koo’s boat and the pair picked up five other friends and headed to Mana Island.
Cao was using the Wolach to free dive for the first time, while others, except Koo, were scuba diving, Coroner Steel said.
The device is described online as a portable, battery-powered surface-supplied breathing apparatus (SSBA).
It used a floating air compressor to pull air from the surface and deliver it continuously to a diver via an air hose and regulator.
Once at the site off Mana Island, Cao attached the Wolach to a buoy and dived several times over the next 10-15 minutes, returning to the boat between dives.
After a while, he mentioned to Koo the Wolach was not working and that he was feeling seasick. By then, he needed help getting out of the water, Koo told police.
Once back on the boat, Cao began to feel better after about 10 minutes, so got back in the water and began diving about 30m from the boat.
The other divers returned to the boat and asked to be taken to another site. Koo tried calling out to Cao and got no response but could see bubbles from his breathing.
Koo left with the other divers. Twenty minutes later, he returned to the spot where Cao had been left but was unable to approach because of the rocky shore, so returned to the other divers.
Only one of that group had surfaced and, concerned about time, Koo waved down a passing boat and told the pair on board he had a missing diver at the location he’d left Cao.
William Rongoa and his son Richmond McGill went to Cao’s location and found his body in the water, still attached to the buoy.
Coroner Steel said the water was about 5m deep.
A breathing tube and pump running from the surface to the diver were attached to the buoy. The mouthpiece, attached to the breathing tube, was not in Cao’s mouth but beside his head.
The father and son retrieved Cao’s body, noticing the Wolach pump was still running.
The coroner said a specialist from the Police National Dive Squad examined the diving equipment Cao was using. He explained that using the Wolach meant a diver was breathing compressed air and was subject to the same rules and physics as scuba diving.
When the device was examined, it was noted that a snorkel was supposed to be attached to the air inlet to prevent waves splashing into the compressor air inlet.
However, the air inlet was damaged, and no snorkel was recovered, the coroner said.
None of those with Cao that day recalled seeing a snorkel attached.
Mana Island lies south of the entrance to Porirua Harbour. The wildlife sanctuary has no permanent human population and is officially defined as a suburb of Porirua City. Photo / Google
The specialist tested the Wolach in a diving pool and found it harder to draw air from the system the deeper he went, because of increased pressure, Coroner Steel said.
The Wolach’s hose was firm when pressurised but shrank when pressure was reduced.
The dive specialist considered it a dangerous system with features that could cause panic or stress in a diver, leading to carbon dioxide build-up, the symptoms of which are dizziness, fatigue, headaches, rapid breathing or shortness of breath.
The specialist also noted Cao had no means of gauging his depth and was therefore “diving blindly” and at risk of decompression illness.
He was also “bounce” diving and using the Wolach as though he were free diving, the coroner said.
She said because Cao returned to the boat complaining of illness, it was possible he was experiencing decompression illness.
A gas embolism found post-mortem supported this, Coroner Steel said.
She said traces of diphenhydramine found in Cao’s blood could have come from seasickness pills but the medication had a sedating effect and should not be used by someone diving.
Problems were also identified with the other dive equipment he had but ultimately Cao’s use of the Wolach, continuing to dive when unwell, and diving alone were all factors in his death, Coroner Steel found.
Tracy Neal is a Nelson-based Open Justice reporter at NZME. She was previously RNZ’s regional reporter in Nelson-Marlborough and has covered general news, including court and local government for the Nelson Mail .
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