MELBOURNE, Australia (AP) — A 13-year-old boy swam for four hours in cold and choppy waters to save his mother and two younger siblings who had been swept out to sea off the coast of Western Australia.

The family, from the state capital Perth, were using kayaks and paddleboards on Friday morning when rough ocean and wind conditions started dragging them out. Teenager Austin Appelbee swam about 4 kilometers (2.5 miles) to shore to raise the alarm, police said.

“The waves are massive and I have no life jacket on. … I just kept thinking ‘just keep swimming, just keep swimming,’” Austin said Tuesday. “And then I finally I made it to shore and I hit the bottom of the beach and I just collapsed.”

Austin said he initially set off in an inflatable kayak and wearing a life jacket, but the ocean was rough and the vessel was taking in too much water so he abandoned it. He then discarded the life jacket because it impeded his swimming. He said he tried to focus on positive thoughts.

The family had set off on their seaside adventure before noon, Austin raised the alarm at 6 p.m. and a helicopter spotted his mother Joanne Appelbee, 47, his 12-year-old brother Beau and his 8-year-old sister Grace around 8:30 p.m.

The family had drifted about 14 kilometers (9 miles) from Quindalup in Western Australia state and spent about 10 hours in the water.

“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,” Police Inspector James Bradley said.

Joanne Appelbee told reporters that she sent her oldest child for help because she could not leave all her children stranded in the ocean.

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

She said she started out feeling confident he would reach the shore but was filled with doubt when the sun started to set and help had still 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.

By the time they were rescued, all three of them were shivering and Beau had lost sensation in his legs because of the cold, the mom said.

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