"I could see a police officer in the water, holding the woman's head up.
"I slipped off some clothing and just jumped in too," he said.
Mr Butcher spent about 10 minutes treading water while he helped the woman.
"It was freaking freezing. As soon as I jumped in, the water zapped all my energy."
A rope was lowered down to the group and Mr Butcher tied it around the woman so she could be winched up to safety.
He believed the woman had sat down on the wharf and then tumbled forward into the water, some time between 11pm and midnight.
"She wasn't talking, she was not coherent," he said.
"She was very lucky. I would imagine another minute in that cold water and I don't know what would have happened."
After the woman was safely out of the water, Mr Butcher managed to pull himself up a nearby boat ladder and climbed to the top of the wharf.
"My energy was completely drained," he said.
He was suffering hypothermia from the cold.
Mr Butcher lost his father in a drowning accident in Taupo, 25 years ago. As the cold began to set in, Mr Butcher found himself thinking about his late father and if he was about to share the same fate.
"Time went by so fast but the water was cold."
His body was still shivering once home.
"My wife said I was an ice block in bed. I'm just glad the woman made it back on to dry land."
Saturday night wasn't the first time Mr Butcher has saved someone from drowning. As a 12-year-old while at a friend's house, Mr Butcher saw a child floating face down in the pool.
He quickly pulled the boy out, saving his life.
A special assembly was held at school to celebrate that act but he quickly dismisses the notion that he is now a two-time hero.
The police officers involved in Saturday's rescue could not be reached for comment.
A Hawke's Bay Hospital spokesperson said the woman was discharged yesterday afternoon.