The couple, both aged 19, were found by rescuers clinging to a tree after falling off the doll on Victoria's Yarra River.
They were told off by police who warned that the blow-up toy was "not a recognised flotation device".
So far 31 people are known to have died in the floods that have hit Queensland, Australia in the last two weeks.
The township of Grantham, 60 miles west of Brisbane, is thought to have been worst hit by the waters which swept through the town without warning.
Meanwhile across Brisbane, 11,700 homes and 6,000 businesses in 50 suburbs were inundated, and a further 14,000 properties damaged as flood waters peaked.
Towns in the southern Australian state of Victoria were preparing yesterday for their worst floods in 200 years.
Residents of Horsham, a town 190 miles north west of Melbourne, were trying to protect their homes with sandbags as the Wimmera River rose more than 13ft.
Wayne Swan, the Australian treasurer, said the flooding along the east coast was the nation's most expensive natural disaster ever. Some estimates say it will cost £12billion. In Queensland, the floods have killed 31 people.
