A search and rescue operation was launched involving police, St John Ambulance and LandSar Turangi volunteers. NZ Forest staff were also deployed and the Taupo-based Greenlea Rescue Helicopter searched from above.
Using the mobile phone, the Greenlea Rescue Helicopter and ground crew were able to log Mr Lucas' general position in the wilderness and, using night vision goggles, spotted him stuck in a narrow, steep-sided part of the river.
"I think he may have knocked himself out and fortunately his friend who followed him down was able to pull him out of the water and do CPR on him," said Greenlea Rescue Helicopter pilot Nat Every.
He said when the helicopter crew first spotted the injured man he was desperately trying to get their attention.
"He was pretty distressed to begin with. He was jumping around and dancing. We managed to calm him down and then started to wonder how we were going to get this guy out."
The helicopter led a ground crew in four-wheel drive vehicles along forestry trails to the closest ridge above the injured kayaker's position.
Rescuers had to go on foot to the river's edge down the steep, bush-covered hillside. Within a short time, Mr Lucas was found on the edge of the river.
A fire that had been lit by his friend was clearly visible and ground teams were able to reach him by 3am, said Mr Shepherd.
Rescue teams began walking Mr Lucas up the steep slope but within a few minutes the plan was abandoned when he started to vomit blood. He was winched out and flown to Taupo Hospital before he being transferred to Rotorua Hospital.
The stricken kayaker, who was suffering from hypothermia, told the helicopter crew his friend had saved his life.
Mr Every said Mr Lucas was recognised as a world-class adventure kayaker and was understood to be the first person to kayak down the falls on a previous expedition.