"The first thing she said to me when I got to her was, 'Thank you, Daddy'. It's a moment I'll never forget."
But as he held Matilda above the water, he realised he was not going to make it back to the beach under his own steam.
"I had one free hand to negotiate the swell, it just wasn't working. [When the waves hit] I was in a line-out position to keep her above the water."
After treading water in the choppy seas for about 10 minutes, he saw two quad bikes driving along the beach.
It was Whirinaki local David Bateman and his family, going for an afternoon ride.
Mr Bateman said he did not see Mr Kersjes and his daughter at first, but stopped because he noticed the Kersjes boys unattended.
"We were asking them, 'Where's your Dad'? It turned out he was out there with his child beyond the breakers."
He jumped off his quad bike, ripped off his hat, shirt and glasses and dived into the water.
"I thought, 'I don't even know if I can make it to him', but then I thought, 'Just do it. It's a job - go and do your job'."
He had reached Mr Kersjes and grabbed hold of him. "I put my hand through his singlet. I said, 'Get on your back and kick'."
As they fought towards shore, a set of waves picked them up and dumped them in shallow water, but the only thing that stopped them being pulled out again was a 5m rope, thrown at them by David's brother, Rex Bateman.
A large wave caused Rex to fall over, injuring his knee. It also swept David's wife, Lisa, off her feet.
"What saved us is Alex grabbed the rope and my wife grabbed his daughter. I felt myself getting dragged back out. I thought, 'I won't make it back in, I haven't got the strength'.
"Then I saw Alex's ankle and I grabbed on to it."
The three exhausted swimmers clambered on to dry land. Soon after, Mr Kersjes collapsed and was taken to Hawke's Bay Hospital. He had swallowed a lot of sea water but has since made a full recovery.
Everyone involved is still coming to terms with the incident.
Rex is nursing his knee and David is having a break from work this week.
"[Alex] could have died. He was quite close," he said. "And quite frankly, I was very close, too. I didn't know if I was coming back in."
He has lived at Whirinaki for a year and wanted to stress it was "not a dangerous beach".
"You've just got to be wary. It's a steep beach, you go out 3m and you go from ankle to neck."
Mr Kersjes, too, was taking a step back.
"Even this morning in the shower I had a moment of panic at what could have been, and what nearly was. It's going to take some time."
He had since travelled back to Whirinaki to thank his rescuers, whom he described as "beyond heroic".
"The kindness of them just to stop because they saw unattended children - I'm forever thankful they were as selfless as they were."
