Jodie Armstrong, 14, was playing with three friends when her foot became struck in the rope and she was turned upside down.
Her head was in the water for half a minute before she managed to wriggle free and fell into the river.
But she was unable to climb out and her friends ran to raise the alarm at a nearby factory where a group of Steelworkers ran to her aid.
Two of them found her and carried her back to their building where they called an ambulance to the scene in Middlewood. Jodie was taken to hospital and treated for severe bruising and a bleeding ankle - but knows it could have been far worse.
She said: “I fell off the rope swing and my foot got tangled around the rope. I was dangling with my head under water.
“I had a lot of thoughts going through my head. I thought I was in danger.
“After about 30 seconds I managed to get loose and fell into the water.
“I was stood in the water in shock after it happened.
“As I sat on the bank, I felt really cold and my ankle was just getting bigger and bigger.”
Friend Kelsea Stancill, 14, said: “It all happened so quickly, I didn’t notice at first that she had gone underwater.
“We were all laughing when it happened but it has made me think about things.”
Jodie’s dad, Gary Armstrong, said: “I was at the cinema with my son when I got a call from my other daughter but I cancelled it.
“Then I got a text saying, ‘call me urgently’ and she said Jodie had broken her leg which is what the paramedics first thought.
“Obviously I knew she was alive but you do start to think of what ifs and what could have been.
“I toyed with the idea of going to cut the rope down, but at the end of the day, it’s part of growing up.
“We’re really thankful to the factory employees for all their help, we took them some beers to say thank you.”