Preliminary post mortem results suggest rafting guide Keith Haare died as a result of a medical event near Queenstown on Friday, police say.
They say the final cause of the 62-year-old's death will be determined by the coroner.
Tributes flowed at the weekend for Mr Haare, of Lower Shotover, an experienced rafting guide who died on a commercial rafting trip on the Shotover River.
Friends of Mr Haare, who was known as "chief", referred to him as a river legend and a backbone of the Queenstown rafting community as they paid tribute on social media.
Queenstown Rafting general manager Luke Taylor said a senior guide from the company had just gone through one of the rapids about half way through the trip.
While recovering an overturned raft he spoke to the dedicated safety kayaker and was shortly after found unresponsive in the water.
Extensive CPR was performed at the scene, including the use of a portable defibrillator, until paramedics arrived, but he did not survive.
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