Austin Appelbee’s family set out on a seaside trip from Perth using kayaks and paddleboards, but rough ocean and wind conditions began pulling them away from shore off Western Australia, police said. In the hours that followed, the 13-year-old swam to reach land and alert rescuers, while the rest of the family remained in the water.

Police said Austin swam for about four hours in cold, choppy conditions and covered roughly 4 kilometers (2.5 miles) to shore. He raised the alarm at 6 p.m. and police said a helicopter spotted his mother, Joanne Appelbee, and his 12-year-old brother Beau and 8-year-old sister Grace at about 8:30 p.m. Afterward, police said all three were found after drifting about 14 kilometers (9 miles) from Quindalup and spending about 10 hours in the water.

In comments Tuesday, Austin described the conditions he faced after being separated from the rest of the family. “The waves are massive and I have no life jacket on. … I just kept thinking ‘just keep swimming, just keep swimming,’” Austin said, AP reported.

He also said he tried to use an inflatable kayak at first, and that he had set off wearing a life jacket. Police said that attempt ended when the ocean conditions worsened and the kayak took in too much water, leading him to abandon it, and Austin said he discarded the life jacket because he believed it impeded his swimming.

Austin said he focused on keeping calm while he swam. He told reporters that “I just kept thinking ‘just keep swimming, just keep swimming,’” AP reported, and that after he finally reached shore, he collapsed. “And then I finally I made it to shore and I hit the bottom of the beach and I just collapsed,” Austin said.

Police Inspector James Bradley said the boy’s actions helped save his family. “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,” Bradley said.

Joanne Appelbee, 47, told Australian Broadcasting Corp that she sent her oldest child for help because she could not leave all her children stranded in the ocean. She said one of the hardest decisions she had to make was telling Austin to reach shore and get assistance, noting that the situation could become serious quickly, AP reported.

She said she started out feeling confident Austin would reach shore but became filled with doubt as the sun 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.

By the time they were rescued, Joanne Appelbee said all three children were shivering and her 12-year-old son Beau had lost sensation in his legs because of the cold. “I have three babies. All three made it. That was all that mattered,” she said.