Mr Nicholson was eventually pulled to safety when two friends and a passerby threw him a life ring, and hauled him to shore. Exhausted, he gasped for breath as one of his rescuers dragged his body to safety.
Tonight, Mr Nicholson told the New Zealand Herald he hoped others would learn from his "dumb arse" mistake.
"What started off as a good idea turned into a very bad idea."
After entering the water at the Port of Greymouth, about 1.5 kilometres from the bar, he saw a mate downstream.
"I got a bit close obviously ... I basically got into a s*** spot and ran out of energy."
Realising he would eventually end up at the bar, where death was certain, he made the decision to bail from his kayak. But a wave washed him away from a friend's outstretched arms.
Unable to reach the tag of his manually-inflatable lifejacket, and choking at his jersey and coat pressed against his neck, waves pounded Mr Nicholson under the water several times.
He thought he was "a goner" until his two friends and bystander dragged him to safety using a life ring, he said.
On shore, but exhausted, Mr Nicholson could barely move.
"I had absolutely nothing left. They definitely put themselves at risk. What can I say? They saved my life today. I'm grateful."
His temperature had dropped to 32C so he was taken to Greymouth Base Hospital to warm up and check for water inhalation, but released a few hours later and acknowledged his good fortune with a beer.
He also had footage of the incident, filmed from a Go Pro camera attached to his helmet, but had only watched snippets, he said.
"I already watched it happen."
Despite the experience, he would probably tackle the river again, but not until he had become more skilled in a new kayak, and not anywhere near the bar.
"A bit more practice and I'll be back."
The Grey River's infamous sandbar has claimed at least nine lives and destroyed many boats in the West Coast town's history.
