Janne Applebee and her three children had been on holiday in Chebucto, about 240 kilometres south of Perth, and set off for Geraldton on Tuesday afternoon before she disappeared.
The family had planned to stop earlier that morning for a picnic on the Bradshaw Causeway.
However, conditions quickly deteriorated, with rough weather forcing them to pull over as they were being drenched by the waves.
Auto said he noticed his feet were covered in mud and managed to guide his family back toward shore using a kayak, before making the heartbreaking decision to send them away for safety.
“I started paddling toward shore on the kayak, but it kept filling with water. The waves were really rough, and I thought there was something in the water. I felt like I was drowning,” he said.
Emergency services later found Autumn nearby, along with her brother Ethan, 13, and her eight-year-old sister Chloe, at about 3:30pm. They were clinging together in the ocean roughly 500 metres offshore.
Rescuers said Autumn’s quick thinking and use of the kayak and paddle shaft helped keep them afloat, praising the effort and describing the rescue team as “heroes.”