Trapped in a concrete coffin and submerged in water, John Purkis thought: “This is it. This is how I am going to go out.”

As the retired policeman drifted in and out of consciousness his survival instincts kicked in and he could only think about his grandson.

“Manaaki is my life. It was quite emotional thinking I wouldn’t see him again. He triggered me to hang in there and not give up. I had to get out of there.”

On January 27, Purkis was swept into a culvert after torrential rain battered the Auckland region causing severe flooding and extreme damage.

Four people lost their lives: Dave Young in Onewhero, Daniel Mark Miller and Daniel Newth in Wairau Valley, and Dave Lennard in Remuera.

Miller, 34, was found dead in a culvert on Target Rd. He had earlier filmed himself walking through floodwater helping residents.

Newth, a 25-year-old surfer and arborist, was kayaking when he was swept into a culvert and died.

That afternoon, Purkis was in the backyard checking the rising water in the creek and clearing debris that might clog the culvert.

Retired police officer John Purkis was swept into a culvert and survived during Auckland's floods in January. The narrow creek behind Purkis's Castor Bay home. Photo / Mike Scott

The 75-year-old was trying to retrieve a pallet and canvas when he was knocked over by a canoe that came out of nowhere. He fell into the water and was swept away.

His grandson, Manaaki 7, was on the upstairs balcony filming the storm oblivious his papa had disappeared and was fighting for his life.

Retired policeman John Purkis, who was swept into a culvert on January 27 and survived, pictured with his grandson, Manaaki Kingi-Thompson. Photo / Supplied

“I clung on to a banana tree, tried to catch a breath and tried swimming underwater but my feet couldn’t reach the ground. I was tumbling and doing forward rolls in the culvert, the depth and sheer force of the water immobilised me, it was horrendous. I was being thrashed around in a washing machine at 100 miles an hour,” Purkis said.

The former detective senior sergeant, who worked at Auckland’s Criminal Investigation Branch, believes 27 years of police training saved him.

Purkis has always loved the sea and dived for kaimoana as a child. He was also a member of a police diving club, which helped with recovering bodies.

“I thought I was stuffed, then my police training kicked in. We did some bloody scary training underwater at night with no oxygen and body recoveries without breathing apparatus so that tests your mettle. I benefited from that training even though it was years ago.”

Purkis, who is familiar with the 86-metre culvert that runs past the local cafe, was worried he would die if he drifted into the second culvert which is twice as long and covered with a metal grate.

As his life flashed before him, Purkis got a lucky break. At the lip of the culvert, he felt a concrete block and used his left foot to lodge onto it, which helped slow him down.

John Purkis was swept into a culvert in Castor Bay during the heavy rains of January 27 and was badly injured. He is pictured in hospital after his ordeal. Photo / Supplied

“I was in and out of the water, felt a brick and thought it can leverage me. I had no idea why I decided to make a move at that point, it was a gift from heaven. I did a superman leap into the air from the water, clung onto the railing and hauled myself over the fence, dropping on the ground. I lay there and was bleeding like a stuck pig. My foot was cut open, my calf had a hole you could fit a golf ball in. My face was bleeding. I looked like a zombie.”

Miraculously, Purkis limped all the way home wounded and bleeding. His daughter, Renell Kingi-Thompson, and her son Manaaki were “spooked” when they saw him.

“I kicked into nurse mode and wrapped him in warm towels and a blanket with wheat bags. Manaaki asked a lot of questions but he was upset and tried to comfort him. I felt sick and angry about what happened to him. He always thinks of others before himself,” Kingi-Thompson said.

Purkis was discharged from hospital last week and has had plastic surgery on his calf, stitches in his head and skin grafts. He is recovering well and is thankful to the medical staff at North Shore Hospital.

“I can’t rave enough about the nurses at North Shore hospital, I fell in love with all of them.”

He is still waking up at 3.30am with a recurring nightmare he is trapped and drowning in the culvert at Castor Bay beach, which is close to where Manaaki likes to dig sandcastles and play with his trucks.

Thoughts of his beloved grandson, Manaaki Kingi-Thompson, 7, helped spur John Purkis into survival mode. Photo / Supplied

“I want people to remember if they are in danger to be rational thinking and not to panic. I know it’s easy to say ‘stay calm and focused,’ it sounds very boy-scoutish but I was a boy scout. I thought I was done for, but I thought f**k this and carried on.”

The waka ama enthusiast can’t wait to get back into water - even though it nearly killed him.

“I don’t blame the water. I am a Pisces man and have been connected to it all my life. I have learned not to sweat the small stuff and just get on with it. I am lucky and grateful to be here and if it was God who saved me then I love him to bits.”