I had never done a bungee jump, but two years ago I decided to give it a go while travelling in Zambia. I was 22 and wanted a big adventure after university, so I'd left Australia for Africa.

I was travelling alone, but I joined a tour group who were going to go bungee jumping over the Zambezi river at Victoria Falls. I'd heard it was incredible – jumping from a bridge 111m over a gorge with the thundering falls behind you.

I felt nervous, but never thought anything could go wrong. I was the 105th person to jump that day. I stood on the platform, looked at my ankles, which had been strapped together, and worried aloud that my feet would slip out. Someone said that would be the last thing that happened.

The view was astonishing, but just before I jumped I thought, "What am I doing throwing myself off a perfectly good bridge?" But I was caught up in the moment, and simply spread my arms and fell forwards. Everything sped by in a blue-green blur. The rush was amazing.

After a few seconds, I felt a jolt across my chest. It seemed as if I slowed down for a second, then sped up. I could hear the wind rushing past my ears. Instinctively, I brought up my arms, locking my hands together. Then I felt myself hit the water – that's when I realised something had gone wrong.

The sound of bubbles was so loud. I felt as if I had been slapped all over. My hands had stopped me hitting the water headfirst and blacking out. My lungs were on fire and I was struggling to breathe.

I later found out I'd fallen for four seconds after the rope snapped: a distance of up to 40m. If I had been over land, I'd have been dead. Luckily, it had rained the day before, so the river was turbulent and full. That morning, I had seen crocodiles in the water, but I couldn't think about that. I was struggling in the fast-flowing rapids, because my ankles were still tied together. The bungee cord had snapped near the top, so I still had about 30m attached to me, which kept getting caught. I was pulled downriver and underwater into whirlpools. At one point, the cord snagged below me and I was trapped below the surface. As I was running out of air and my vision started to fade, I managed to dive back down, grab the rope and pull it free. Eventually I managed to wedge my arm between two slimy rocks near the side of the river. All I thought about was clinging on.

I now know I was in the water for 40 minutes. The first guy to reach me was from the bungee company. He grabbed my harness and got me straight out of the water, giving me his shirt because I was shivering. I was worried that he didn't have first aid training, so I got into the recovery position. Then I started throwing up water from my lungs. My body was purple with bruises from the impact. I started coughing up blood and began to worry about internal injuries. I felt exhausted and struggled to process what had happened.

I jumped at 5.30pm and didn't get to hospital in Victoria Falls until 11pm. The paramedics got lost, and because I'd ended up on the Zimbabwean side of the river without a passport, I was essentially an illegal immigrant. I was put on a ventilator, and needed an ultrasound and to see a lung specialist. They gave me a large dose of antibiotics – the doctors were worried about how much dirty water I had ingested. X-rays showed no broken bones, but my lungs had partially collapsed. The guys from the bungee company visited me in hospital. They were very apologetic and astounded I'd survived. Facilities were basic, so I had to be flown to South Africa. Friends I'd met travelling got me my belongings and passport, so I could travel. Two weeks later, I went home.

I'm a positive person, so I've never been angry about what happened. Around 50,000 people jump from that spot every year, so it was pure chance that the rope snapped on me – just wear and tear. They've now introduced measures to ensure it doesn't happen again.

I called Mum and she bought a plane ticket straight away. I'd sent her a postcard the day before, saying, "I'm doing a bungee jump tomorrow, so I'll say goodbye… only joking!" which she now keeps on the fridge. She's adamant I'll never do another, but I'm not so sure.

• As told to Sophie Haydock

Do you have an experience to share? Email experience@theguardian.com