A 13-year-old boy has saved his mother and two younger siblings by swimming for four hours in fading light and rough conditions, after they were swept out to sea in south-west Western Australia.

The family were holidaying in Quindalup, 200km south of Perth, when strong winds pushed their inflatable paddleboards and kayak offshore from Geographe Bay on Friday afternoon.

The boy attempted to kayak back to shore to get help, but the vessel took on water, forcing him to swim 4km back to shore, where he successfully raised the alarm.

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Western Australia police received a report at 6pm on Friday that a family had been swept out to sea, and a multi-agency search and rescue operation was mobilised – including WA water police, local marine rescue volunteers and Western Australia’s rescue helicopter.

The woman, 47, a boy, 12, and a girl, 8, were located by the rescue helicopter at 8.30pm, clinging to a paddleboard.

A volunteer marine rescue vessel was directed to their location and all three were successfully rescued.

Map of WA

Naturaliste Volunteer Marine Rescue’s commander, Paul Bresland, said the family was located about 14km offshore and had been treading water in rough seas for hours before they were found, the ABC reported.

Bresland said the 13-year-old gave a detailed description of the colour of the kayaks and paddleboards – invaluable to search efforts.

He also revealed that the teenager swam for two hours with his lifejacket on, before taking it off and swimming another two hours without it.

St John WA paramedics assessed the family before they were taken to Busselton health campus.

A spokesperson for St John WA said it was a “remarkable rescue” and praised the teenage boy for his “brave actions”.

The family were taken to Busselton health campus for medical assessment. Photograph: Michael Evans/Alamy

Police inspector James Bradley thanked those involved in the successful rescue mission and said it was a reminder that ocean conditions can rapidly change.

“Thankfully, all three people were wearing lifejackets, which contributed to their survival,” he said.

“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.”