And more than 13 years later he's still living most of his life around the water and using his story to save others from falling foul of the mighty ocean.
The brother of former All Black Norm Hewitt was diving with mates off the Kapiti Coast when caught in a rip in February 2006.
He surfaced 600m behind their boat and was quickly pushed further away by the tide.
Over the next 75 hours he became extremely cold and severely dehydrated, his skin was nibbled by sea lice, he suffered hallucinations and he made two half-hearted attempts to end it all.
He survived by eating kina and crayfish and sucking watery mist from his oxygen tank.
"There was no worry," the former Navy diver told the Herald on Sunday soon after his ordeal.
"It was 'oh well, I'm a good swimmer, I've got all my gear on, I'm not going to die. I'm sweet as. Just wait. Someone will come.' "
But for an age, no one did.
It was his mates who eventually came to his rescue.
Navy chief petty officers Lyle Cairns and Buzz Tomoana were out on an inflatable boat searching for Hewitt - assuming they would find him dead - when they spotted him floating in a sheltered cove.
He was just 300m from where he went missing.
They knew he was alive because he was vertical in the water.
"We both looked at each other saying this can't be happening and there was Rob Hewitt looking straight at us," Cairns told the Herald on Sunday.
Following the dramatic rescue, Hewitt penned a book titled Treading Water and a documentary was filmed about his ordeal.
These days water is still firmly in Hewitt's daily life.
Initially, he said he was reluctant to go near the ocean, but he soon got back on the horse.
"I think it was inevitable I would move back into this space," he said.
"After my survival, I tried a few things here and there - I managed a rugby league team, I tried to stay inland rather than coastal.
"I went for that old attitude of once bitten, twice shy - but then I had to push through it." Hewitt is now on the board of Water Safety New Zealand and works for the body as a Māori water safety advocate and educator.
His role is all about connecting health and wellbeing around the water to Maori and Pacific Island people.
His goal - to prevent drownings any way he can.
"I talk to them about putting on their spiritual lifejacket before their actual lifejacket," he explained.
"That could be saying a karakia before going into the water, telling someone where you're going, checking your gear, checking the environment, the weather before you put that actual lifejacket on.
"I'm alive and everything is good - if you're got a story to tell then people are going to listen."