'A great, grey wave sucked me towards it and then broke across me like a sack of gravel, bouncing me along the seabed'

I would happily never have set foot in the Atlantic that weekend. I'd heard about the riptides just off the North Cornwall coast, and was used to swimming in the calmer waters near my home in East Sussex.

My brother-in-law was a keen surfer, though, and determined to convert me. The first morning of our visit, I was zipped into a wetsuit and marched to the water's edge. Like most first-time surfers, I quickly decided I was a natural, riding three large waves on my hands and knees. The current was far stronger than I was used to and I had moments of sudden panic – perhaps I should have taken them as a warning. But exhilaration won out, and when we visited a small cove farther up the coast the next day, I was keen to get back in the water.

As the light began to fade, I felt compelled to have a last dip before we headed home. The waves had become choppier as afternoon eased into evening, but still appeared harmless enough from the shore. I plunged in and struck out, confident at first, realising my mistake only when I was out of my depth. The surf dragged at my legs, hauling me down, and rocks hidden below the surface grazed my knees and elbows as I tried to fight my way back to the beach.

A great, grey wave sucked me towards it and then broke across me like a sack of gravel, bouncing me along the seabed. Desperate for air, I was churned around until I no longer knew up from down. Then the current relaxed its grip and up I went, just in time for the next big wave to break over my head and push me back under.

Each time I surfaced, the process repeated itself, until I was battered and winded, and still out of my depth. I swallowed water, tried not to breathe it in, waved frantically at the party on the beach. They were packing bags and chatting, paying me little attention. Once or twice, someone waved back.

From their perspective, it probably looked as if I was larking around, diving into the waves; waving but certainly not drowning. I'll never read that poem again, I thought. Then it really struck me that I was actually about to drown and no one knew. I experienced an acute sense of loneliness and isolation as another wave thrust me down.

I thought of all the stupid risks I'd taken without consequence, only to find myself overwhelmed in a moment of relaxation. In my work, I'd interviewed lots of people who had been in near-death situations; some had mentioned fear and panic, others a sense of resignation. I just felt overwhelmed, helpless and undignified, like a sock in a washing machine. Rather than fear, I experienced sadness: it's all very well dying doing something you enjoy, but this had been the least enjoyable swim of my life.

As I struggled, an intense pain bloomed at the top of my chest, spreading downwards and inwards. That's my lungs giving out, I thought, or my heart. Back on the surface I tried to wave again, but I couldn't lift my arm and the pain became intolerable. I finally found myself able to breathe, but it only made the pain worse.

The next wave offered some relief, though, driving me towards the shore. My feet found a purchase at last and I stumbled forwards, my right arm dangling at my side. My brother-in-law, realising something was wrong, ran into the shallows to guide me on to the beach. "You've dislocated your shoulder," he said. Looking down, I could make out the strange peak at the top of my chest where my arm joint, torn clean out of its socket during the struggle, was protruding beneath the skin.

I sat on the beach, wrapped in a towel, shivering. Someone brought me coffee, but I was suffering from shock more than cold. Breathing became increasingly difficult. I'd escaped the sea but now felt as if I was drowning on dry land.

I managed to gulp down the gas and air in the ambulance – nearly a whole canister on the hour-long journey to hospital, where most of the pain eased in an instant as my shoulder was popped back into place by a nervous-looking orthopaedic doctor. Months of physiotherapy helped the damaged muscle but nothing could rebuild my carefree attitude to water – the thrill of being at one with nature replaced in an instant by the sense of being at the mercy of an irresistible force. Even small waves fill me with apprehension now. There's a sea pool in Bude, a lido offering sanctuary from the tides – I swim only in there, and stick to breaststroke.

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