Before emergency services arrived, the men jumped into the murky tidal creek and pulled two occupants from the vehicle.
A third occupant, Janice (Jan) Fa'avae, 68, died at the scene.
Senior Station Officer Davies, who nominated the men for a Pride of New Zealand award and was in charge of the crew who attended the accident, said the four risked their own safety to save others' lives.
"We were really lucky to have those people in Nelson at that time."
The men saw the car go across the road in front of them and into the creek, Mr Davies said.
It was a cold, mid-winter day, but that didn't stop them from jumping into the water, he said.
When the young boy was pulled out of the water and passed to Mr Davies, he wasn't breathing.
"That's how fine a line it was between life and death.
"This boy had another couple of seconds to go, it was that close. These guys absolutely saved his life." Susan Strongman