A 13-year-old boy who was swept out to sea with his family swam for an incredible four hours to get back to shore on Western Australia’s south-west coast and raise the alarm.

Austin Appelbee is being praised as a “superhuman” hero for saving the lives of his mother Joanne Appelbee, 47, and two younger siblings Beau, 12, and Grace, 8, who had drifted 14 kilometres in the ocean.

The family, from Perth, was on holiday in Quindalup, about 250 kilometres south of the state capital, last Friday morning.

They were using kayaks and paddle boards hired from their hotel when rough ocean and wind conditions started dragging them out to sea.

“The wind picked up and it went from there. We lost oars, and we drifted out further…. It kind of all went wrong very, very quickly,” mum Joanne told the BBC.

She had to make the difficult decision to send Austin back to land — a vast distance — because he was the strongest and the most likely to make it.

Austin said he initially set off for help on an inflatable kayak, but it was taking on water. He abandoned the kayak and then also took off his life jacket because it impeded his swimming.

He then swam for about four hours through rough seas, trying to focus on positive thoughts.

“The waves are massive and I have no life jacket on. … I just kept thinking ‘just keep swimming, just keep swimming’,” Austin said on Tuesday.

“I finally I made it to shore and I hit the bottom of the beach and I just collapsed.”

He found his mother’s bag and used her phone to call for help.

A search helicopter found the mother and two children wearing life jackets and clinging to a paddleboard at 8.30pm local time, police said. They had drifted 14 kilometres from Quindalup.

“The actions of the 13-year-old boy cannot be praised highly enough — his determination and courage ultimately saved the lives of his mother and siblings,” WA Police Inspector James Bradley said.

Joanne Appelbee said she sent her oldest child for help because she could not leave the three children.

“One of the hardest decisions I ever had to make was to say to Austin: ‘Try to get to shore and get some help. This could get really serious really quickly,'” she told the ABC.

She said she was confident the teenager would make the land but became doubtful as the sunset set and help had not arrived.

“We kept positive, we were singing and we were joking and … we were treating it as a bit of a game until the sun started to go down and that’s when it was getting very choppy. Very big waves,” Joanne Appelbee said.

All three were shivering and 12-year-old Beau had lost sensation in his legs because of the cold by the time they were rescued, she said.

“I have three babies. All three made it. That was all that mattered,” she said.

All four family members were medically assessed but none required hospital admission.

Austin said he did what was needed to save his family.

“I didn’t think I was a hero — I just did what I did,” he told the BBC.

-with AAP