Austin Appelbee is still trying to process his superhuman effort to save the lives of his mum and two younger siblings, who were feared dead after they spent more than eight hours clinging onto paddleboards in the open ocean off WA’s south coast.

The hero 13-year-old undertook a gruelling 4km swim back to shore on Friday afternoon to raise the alarm with mum Joanne, brother Beau, 12, and eight-year-old sister Grace fighting for survival and drifting out to sea off Dunsborough in Geographe Bay.

The family’s fun day on the water turned into a nightmare as conditions gradually worsened from 11am, causing them to lose paddles and their kayak to take on water and start sinking.

Knowing they were out of options, Ms Appelbee was forced to make a heart-wrenching request of her eldest child.

“One of the hardest decisions I’ve ever had to make was to say to Austin, ‘Try and get to shore to get some help’, because it was getting serious really quickly,” she said on Tuesday.

For the next four hours, Ms Appelbee was tormented by whether Austin had made it to shore and whether she had made the right decision, while also trying to keep up the spirits of Beau and Grace.

“As the sun went down I thought, ‘Something’s gone terribly wrong here’, and my fear was that Austin didn’t make it … everything goes through your head,” she said.

Meanwhile, Austin was fighting demons of his own and after spending two hours battling with his kayak and getting nowhere, he decided he would be better off without it.

“I knew it would be a long way but the kayak kept taking on water, I was fighting rough seas, the kayak dumped me a million times, I thought I saw something in the water and I was really scared but I was just thinking I was going to make it,” he said.

Austin rotated between survival backstroke, breaststroke and freestyle for the next two hours, showing remarkable mental resilience as well as physical endurance.

As he made his way closer to land, he distracted his mind with happier thoughts.

“I was thinking about all my friends at school and friends of my Christian Youth and I just said, ‘Not today’,” he said.

“At one point I was thinking about Thomas the Tank Engine, just trying to get the happiest things in my head.

“I’ve got a girlfriend and I was thinking about her the whole time. She gave me her hair lackeys and I was just looking at that the whole time.”

When he eventually made it to solid ground, Austin said his legs “collapsed”.

But he knew he had to dig deep again and miraculously hit the ground running for about 2km to Club Wyndham Dunsborough to find his mum’s phone and make the most crucial call of his — and his family’s — life.

At the other end of Austin’s triple-0 call, local rescuer volunteers knew right away they had a major challenge on their hands.

Finding the trio who had been drifting for hours would be difficult but setting out to do so in rough conditions and with the sun beginning to set meant the odds were against them.

Naturaliste Volunteer Marine Rescue commander Paul Bresland and skipper Dan Crosbie conceded that at the time, the chance of finding any survivors was slim.

“With the massive offshore wind and the time frame, we knew it was going to be out to sea, so we started searching out a bit wider,” he said.

At 8.40pm, the helicopter spotted the family. They had drifted about 14km out to sea.

Mr Crosbie said finding the family alive was a massive relief.

“With hypothermia, survival after six hours is not common, so this was a very good news story, a great outcome,” he said.

“It’s what we were all hoping for but we were preparing for a recovery, not a rescue. We’re all a bit emotional.”

A matter of minutes before the rescue, the situation took a distressing turn when a big wave hit the family, separating them.

“I could only hear Grace screaming. I couldn’t hear Beau, and that scared me,” Ms Appelbee said.

“When the boat came and picked me up, I screamed that there was two kids in the water.

“I called out for Grace and I could hear her, and then all of a sudden I heard this other voice (Beau).

“We picked them up and it was the best feeling in the world.”

The family were taken to Busselton Health Campus and aside from blistering, swelling and muscle pain, avoided injuries.

Austin is still pretty sore and rocked up to school on Monday to share his incredible tale in a wheelchair.

He has since swapped the wheelchair for support crutches and was ecstatic when his bravery scored him an invite to meet his favourite AFL team, the West Coast Eagles.

The family have extended their immense gratitude to the multi-agency rescue mission involving the Water Police Coordination Centre in North Fremantle, South West police, local marine rescue groups and the RAC Rescue helicopter.

They plan to meet and thank those responsible for saving them.