A group of men tossed from their jet boat into icy water swam up to 1km to the shoreline before the youngest member battled rugged terrain to find help.
The two remaining men were whipped by strong winds of up to 20 knots and pelted with rain as they waited on the remote and rugged Fiordland coastline up to four hours for help.
One of them would not survive.
While darkness fell, the third member of the group pushed his way through rough, rugged terrain to seek help, eventually raising the alarm 2km away at the remote Waitutu Lodge.
Te Anau Police Sergeant Tod Hollebon said the three men had left the Waitutu River and were heading about 12km around the rugged coastline to the Wairaurahiri River when the boat was swamped.
The were thrown into water about 1km west of the Wairaurahiri River mouth on the south coast of the South Island between 3pm and 4pm.
It is understood they spent about an hour in the sea. All were wearing lifejackets.
Due to the remote and rugged location, it took another three to four hours for one of the boaties to raise the alarm.
With no cellphone reception, the managers at Waitutu Lodge radioed to the closest rural town Tuatapere for help who in turn contacted police at 7.15pm.
"A very well established comms set up but one that is not at all relying on phone coverage."
Te Anau-based Southern Lakes Helicopters flew a paramedic and a police officer to rescue the other two men.
Hollebon, who was the police officer onboard, said due to the directions they had been given they were able to quickly locate the two men still on the coastline.
On arrival they found one of the men had died and the other was freezing from sitting in the bitterly cold conditions.
"He was understandably cold," Hollebon said.
The helicopter picked up the survivor on the coastline and the other survivor who was being cared for at Waitutu Lodge before transporting them to Invercargill Hospital.
"They were very cold and had clearly suffered an ordeal. Quite exhausted actually. They have done really well to get through that."
A second helicopter was called to transport the body. Pilot Richard Hayes said conditions were difficult.
"It was dark. It was a night vision goggles operation."
It was high tide and the beach was too steep to land the chopper on so Hayes balanced the aircraft while three crew members retrieved the body, which was then flown to Invercargill Hospital.
Given the conditions, the two surviving men were lucky to be alive, Hayes said.
"They were in the water for about an hour. The water temperatures are pretty low along that south shore at this time of year. There was a bit of a sea running too.
"I guess the other two were quite fortunate that they survived."
The death had been referred to the coroner.
The men, from the South Island, has been visiting Fiordland National Park located in the south west of the South Island. The area is extremely remote and the only access to the area is a walking track, jet boat or helicopter.
They had been travelling as part of a larger group with three jet boats in total.
However the other jet boats were not with them when the boat flipped and had been unaware they were in trouble.
Police were still making enquiries into what the group had been doing in the area and what caused the vessel to capsize.
Hollebon praised the lodge managers for their help and said if the third occupant of the boat hadn't gone for assistance they could still be missing.
"He did well to find his way back to the lodge and raising the alarm and assisted in saving the survivor - the person left at the scene," he said.
"From what I saw, if that person hadn't made it to raise the alarm then you know it may have been a lot more serious. They may not have been reported missing for some time."