He told his mum to call the emergency services before running down to the river bank.
By the time he got there, the girl was being swept away.
He started running along the bank yelling instructions to keep calm and try to get on to her back.
"Then she got sucked under the water."
At that point he knew he would have to ditch his school uniform and dive in after her.
Luckily, New Zealand sports champion Jeremy McKenzie appeared on the scene and could help Mr Pauley.
"It was me holding on to Tenishya and holding on to him, and him holding on to a flax bush.
"Then the whole flax bush got pulled out of the riverbank and we got swept away again," Mr Pauley said.
The trio were pulled back into the rapids but Mr McKenzie's encouraging words gave Mr Pauley extra fight.
"I remember him saying 'Come on, we need to get her in', and having him there saying that triggered for me a 'yep, ok we can do this'."
Mr Pauley held the girl above surface as Mr McKenzie guided them into an area of still water.
Once ashore, the emergency services were waiting to treat the girl and her saviours.
People came out of their houses with blankets and passers-by stopped to watch.
"I was standing there in my underwear and my socks and a couple of girls' college students were around, which wasn't great on a cold morning like that," Mr Pauley joked.
Mr Pauley, a former Marlborough Boys' College head boy, now in his first year at Otago University, has been nominated for a Pride of New Zealand Award, in the Bravery and Heroism category.
Mr Pauley said the term "hero" is often thrown around and he is certain that anyone would have done what he did in the same situation.
The community response was overwhelming, he said.
He received 400 Facebook messages from strangers, a stream of gifts and cards were sent to his school and people stopped him in the street.
A week after the incident, he and Mr McKenzie met Tenishya.
She gave them each a pair of Superman boxers and a certificate.
"It was the first time a girl has ever bought me underwear - so that was really cool." Eva Corlett
