Tim Holmes yesterday told how his wife Tammy and their five grandchildren huddled in water under a jetty for 2½ hours to avoid the fire which destroyed the couple's home in Dunalley, Tasmania.

Mr Holmes and his wife were looking after grandchildren Matilda, 11, Liam, 9, Caleb, 6, Esther, 4, and Charlotte, 1, while their mum Bonnie and dad David were out.

Mr Holmes thought he had prepared his property for Friday's bushfire, but when he saw smoke rise from a nearby ridge, he sent Tammy and the grandchildren to the nearby sea jetty.

Despite the arrival of three fire trucks, the 62-year-old could not defend the home he built himself.

"I looked at the firefighters and said, 'I have to go to Tammy and the kids'." Mr Holmes ran downhill and found Tammy and the five grandchildren huddled in the water, their pet dog Polly on the jetty.

"For the next 2½ hours we huddled under the jetty as the fire intensified and produced a plume of smoke, ash and debris that left us with very little oxygen," he said.

"There were times when we had to move out deeper because it was too hot, and there were times when the jetty itself caught fire.

"I was able to scoop some water onto the jetty and put it out."

They eventually made their way to safety as the fire burnt itself out.

"It's all gone, every last item, but it's a great sense of relief to think that we lost not one hair on a child's head," Mr Holmes said.