A warning has been issued to divers after a South Australian man using a "hookah" breathing device suffered carbon monoxide poisoning and drowned.
State Coroner David Whittle issued a public statement on Wednesday after opting not to hold an inquest into the 31-year-old's death.
He found the man had died of carbon monoxide toxicity with drowning after failing to emerge from the water while diving with friends from a boat.
Mr Whittle said the man had been using a "hookah" device which supplies air to a diver via a hose from a compressor fuelled by a petrol engine.
Two members of the group had attempted to use the device but returned to the boat because it was providing insufficient air.
After further checking, the man dived into the water alone.
His friends tried to bring him to the surface due to a change in the weather but found him unresponsive. They performed CPR but he could not be revived.
The hookah system was inspected and found to be "generally poorly maintained, with significant faults".
Its pressure relief valve and regulators were not operating correctly and an air quality test found the unit was delivering a high level of carbon monoxide.
"The exhaust pipe of the petrol engine was in a poorly ventilated part of the boat and the intake pipe for the air compressor was just above the engine exhaust," the statement issued on Mr Whittle's behalf said.
"The exhaust was the source of the carbon monoxide delivered to the deceased diver.
"The State Coroner wishes to alert persons using hookah systems of the necessity for safe ventilation of engine exhausts and placement of air intakes, as well as the need for regular expert maintenance and servicing."
The coroner's office did not release details about the man's identity or when he died.
