A Taiwanese tourist almost drowned after accidentally walking off a pier in the Australian city of Melbourne while checking her Facebook page, media reports say.

The woman tumbled from St Kilda's pier into Port Phillip Bay late on Monday night, BBC reported.

Police were alerted to the incident by a witness and rescued her in a speedboat after about 20 minutes.

The woman was taken to hospital for observation but police said she was fine.

Senior Constable Dean Kelly of the water police said officers found her floating metres from the pier.

"She was still out in the water laying on her back in a floating position because she told us later that she couldn't swim," the Australian Broadcasting Corporation quoted him as saying.

"She still had her mobile phone in her hand and initially she apologised... she said 'I was checking my Facebook page on the phone and I've fallen in'."

While laying on her back and floating on the current, she presumably chronicled the whole incident on Facebook as she bobbed with updates like, "I am in the sea. #drowning #cantswim", according to the Inquirer.

Victoria police told reporters that the tourist was lucky to be alive but added with true Aussie tongue in cheek: "There will be no need for a lost property report as the woman kept hold of her mobile phone throughout the entire ordeal."

Constable Kelly called on people to pay more attention when using social media around water.

Enterprising developers have already come up with several apps that could have prevented the incident, by utilising the camera to create a transparent 'window' on the phone screen so you can walk and chat to your heart's content, the Inquirer reported.