"She was panicking -- who wouldn't be panicking.
"I kept going under. The biggest thing was trying to keep my daughter above water.
"The waves kept getting to us, I thought that was it, I had no energy whatsoever.
"I didn't think I was going to make it."
He said the "last time" he was going down, his feet touched sand.
"It was a blessing."
He was helped out of the water, exhausted, by beachgoers, including an "amazing guy" whose name he didn't know.
"He took the weight off my shoulders."
He passed out when he was on the beach.
Police said both Mr Alaimoana and Ethan had to be resuscitated.
A family member and an off-duty doctor staying at the beach performed CPR on the boy, who was in a "pretty bad way", police Constable Dana Johanson said.
"He was very grey and not responding and unconscious."
Mr Alaimoana regained consciousness fairly quickly, she said. The successful rescue could be put down to some quick thinking by locals.
"It was really good community action and that's probably why the guy is alive."
Masterton Senior Sergeant Mike Sutton said all those at Castlepoint who helped the family deserved to be praised.
"The 12-year-old boy who was in the most serious condition was able to walk to the rescue chopper, so that was fantastic work by the people out at Castlepoint.
"They did great work to save four lives, or certainly two. And the whole family as well -- they looked after each other.
"It was a pretty stressful situation for a while there."
It was unclear how long the family were fighting the rip, he said. "What might have been a couple of minutes might have seemed like a lifetime."
Mr Alaimoana was airlifted to Wairarapa Hospital with his son, while his daughter came separately in an ambulance.
He said emergency services were "really supportive". It was an emotional time but his story had a happy ending, he said.
"[There's] too many sad stories about drowning."
His children had kept him going, Mr Alaimoana said.
"I would have sacrificed myself for them any day."
