Let this be a cautionary tale about walking and staring down at your phone . . . it can be REALLY dangerous.  Of course, we know this will have ZERO effect on anyone's behavior, but whatever . . . we can try.



On Monday night, a female tourist was walking down a pier in Melbourne, Australia . . . and checking Facebook on her phone.



And she was SO ENGROSSED with Facebook that she stopped paying attention to where she was going . . . and walked RIGHT OFF THE PIER.



Turns out she couldn't swim . . . so she just floated on her back in VERY COLD WATER for about 20 minutes until the cops could fish her out.



She admitted she'd walked off the pier while checking Facebook, and they took her to the hospital, where she was treated and released.



And even though the water almost definitely destroyed her phone, the cops say she, quote, "kept hold of her mobile phone throughout the entire ordeal."