A new report into the death of a tandem skydiver in Queenstown has found the operator's safety plan had no regard for how long people could survive in cold water.

Tyler Nii died in a skydiving accident in 2018. Photo: Supplied

Tyler Nii, 27 of California, died after the main and reserve parachutes failed and he hit Lake Wakatipu with his tandem master on 10 January, 2018.

The tandem master survived but Nii's body has never been found despite extensive searches.

The Transport Accident Investigation Commission investigation found unsuitable lifejackets had been used in parachuting and the parachute likely was not packed correctly.

TAIC chief investigator of accidents Harald Hendel said the tandem rider's lifejacket did not properly inflate, but had never recovered it to determine why.

"The Commission never recovered the rider's lifejacket and couldn't conclusively determine why it only partially inflated. But we did identify a risk that lifejackets certified for parachuting have been unsuitable for parachuting conditions," Hendel said.

"The Commission found the main chute's uneven opening and twisted lines - a hazard that parachutists anticipate and practice for - was likely due to its packing. We couldn't conclusively determine why tension knots appeared in the reserve chute's lines."

"Another key issue was that the operator's water emergency response plan had no regard for the anticipated time that people can survive in cold water; that's a problem because it increased the likelihood that rescuers would arrive too late to save lives."

The skydive was proceeding normally until the main parachute opened unevenly with twisted suspension lines.

The tandem master cut away the main chute and deployed the reserve when he couldn't correct the line twist.

The canopy of the reserve chute was distorted by some shortened suspension lines, causing a fast spin.

The tandem master managed to ease the spin rate, reducing the force of impact, and getting Nii to put on his lifejacket just before they hit the water.

He dived underwater, cutting away lines tangled around their legs and tried to unsuccessfully to inflate Nii's lifejacket.

Rescuers saved the tandem master but could not find the Nii, the attached harness and the lifejacket.

The Commission recommended some Civil Aviation safety rules and equipment standards for unintended water landings be reviewed and improved by a working group between the Ministry of Transport, Civil Aviation Authority and the country's two Parachute Recreation Organisations.

In particular, the Commission suggested that the group should specify flotation devices that were suitable for use by parachutists.

TAIC also recommended that the Civil Aviation Authority review its system for reporting parachute accidents and incidents, to inform decisions that make parachuting safer.

"To all parachutists, we're saying accidental landings in water are possible and riskier than you might think, so it's vital that you practice doing it," Hendel said.