A New Zealand coroner has called for a tankless diving device to be banned after a freediver drowned while using it, while recommending a wider review of similar systems sold to consumers.
The Wolach 919 tankless diving system as displayed on the online trading platform Alibaba.com
A New Zealand coroner has recommended banning the importation of a consumer “tankless” diving system after a 58-year-old freediver drowned while using the device off Mana Island, near Wellington.
Shengwei Cao died on 5 March 2023 while using a Wolach 919 surface-supplied breathing unit bought online. Coroner Amelia Steel ruled his death an accidental drowning, with decompression complications contributing.
Inconsistent air supply
Unlike scuba, the Wolach system uses a battery-powered compressor at the surface to supply breathing gas through a hose. Cao was an experienced freediver but had no scuba training and was using the unit in open water for the first time.
Testing by a specialist from the New Zealand Police National Dive Squad subsequently found that the equipment could produce an inconsistent air supply, particularly at depths around 4.5–5m.
According to evidence reported from the coroner's findings, the compressor did not activate until pressure in the breathing line had fallen sufficiently, making it increasingly difficult to draw a breath. The police specialist considered the system dangerous.
Cao had reportedly complained that the equipment was not working properly and felt unwell during the outing, but later returned to the water. He was eventually found at about 5m depth, still attached to the floating unit.
Wider concern over tankless systems
The coroner recommended that New Zealand's Ministry of Business, Innovation and Employment (MBIE) ban imports of the Wolach 919 and investigate the availability, risks and regulation of similar consumer devices.
The distinction is important. Surface-supplied breathing equipment is well established in diving, and the case does not suggest that such systems are inherently unsafe. However, breathing compressed gas underwater carries physiological risks whether the gas comes from a cylinder or a surface compressor.
Divers Alert Network notes that hookah divers can face many of the same hazards as scuba divers, including decompression sickness and pulmonary barotrauma.
Other factors were also identified in Cao's death, including diving alone, lack of scuba training and continuing to dive after feeling unwell.
MBIE says the Wolach 919 is not currently being sold in New Zealand and is considering the coroner's recommendations. No wider prohibition on tankless systems has yet been imposed.
