Corrine Kamara, 18, had been throwing sticks for her dog when she became trapped in the mud, near Hammersmith Bridge.
"I was bent awkwardly forward by the force of the mud and nearly totally submerged. It was only then that my phone bleeped on low battery and I realised I even had it," she said. "It was a struggle to reach it because one arm was already submerged and I was trying to stop my face going under with the other one."
She managed to dial 999 and tell the operator roughly where she was before the phone went dead.
Ms Kamara (pictured) said: "The worst moment was when the police boat went straight by me. That's when I really thought I was going to die. I didn't know there was another boat and any way that didn't find me for another 15 minutes. By this time both my arms were trapped in the mud."
When rescuers found her, a police officer crawled over the mud using a stretcher for buoyancy which he then used to prop Ms Kamara's head out of the mud. She was freed 90 minutes later and taken to Charing Cross Hospital where she was treated for pulled ligaments in her leg, hypothermia and the effects of swallowing mud.