Don Reid completed the 12.3km swim from Motiti Island to Maketu in four hours and 15 minutes, a personal best for his little boy.
He was joined by Chiefs and All Blacks hooker Nathan Harris, Chiefs teammate Toni Pulu, and strength and conditioning coach Phil Healey in the swim to help raise money toward the $150,000 needed to send James to the United States for surgery.
James suffers from spastic quadriplegia cerebral palsy and also has hydrocephalus (water on the brain) as well as epilepsy.
Click here to read about his family's journey.
It was the third time Reid had completed the swim, and not having done the swim in 18 years, he was proud of his efforts.
Reid, who jumped in the water at 6.11am Saturday, was joined by about 40 others for the crossing. He completed it in four hours and 15 minutes. The fastest time he had completed the crossing previously was 4.35 hours in 1997.
Harris said it was great to see the amount of community support for James.
"I know his parents were stoked," he said.
James's mum Sonja Reid said there had been a huge turnout on the day - about 1000 people came out for the event.
It looked like there was a little bubble of Maketu because everywhere else it was pouring down. We were very lucky and blessed.
The fastest time recorded on the day was made by Todd Rowan who swam the crossing in 3.55 hours, the quickest time in history.
Mrs Reid said the day was unbelievable.
"I'm so proud and it was emotional. It was incredible. The whole of Te Puke and Maketu got behind us all. When I was driving over there at 8.30 in the morning it was raining hard and I just thought, 'Oh no'.
"But someone must have been looking after us because the rain stopped and the sea went crystal clear and calm and you could see they had really good visibility out there. It looked like there was a little bubble of Maketu because everywhere else it was pouring down. We were very lucky and blessed."
Mrs Reid said James had been blown away at his father's efforts from the swim.
"He wanted to see his dad come in from the swim and see the band so that is what we did - he was super excited to see him [Don] coming out of the water. Then he was like, 'Right, let's go to the band'."
Yesterday afternoon the Givealittle page used to raise money for James had reached more than $25,000 but was expected to reach more than $35,000 after everything had been added up from the weekend.