In his autobiography, Chance Witness, the writer and broadcaster Matthew Parris recounts how as a young Tory MP he once leapt into the Thames to rescue a stranger's dog. It was winter, the water was freezing and he immediately lost all strength in his limbs. Despite being a strong swimmer, he almost drowned. "Reader," he wrote, "do not do what I did."
I had a similar experience 10 days ago, but in very different circumstances. I went for a swim off a deserted beach 100 kilometres south of Dar es Salaam in Tanzania. It was windy, the sea was choppy and the tide was going out – all factors that should have set alarm bells ringing, but didn't.
I dived through a couple of waves and then began swimming out. Despite the rough sea, the water was warm, a delicious novelty for an Englishman. A few minutes later, I looked up and saw I was already 100 metres down the coast and 40 to 50 metres out.
I started back towards the shore, but it was rapidly clear I wasn't making much progress. Once in my life, I had been in a similar situation – struggling to swim against a powerful rip current – but that was 40 years ago on the southern shore of the Caspian Sea in Iran. I am a reasonable swimmer, but my ageing limbs tire quicker now.
I began to panic. As the sensation rose, I felt my strength drain away. I knew I had to suppress it. At one point, I even yelled – uselessly, as there was no one within earshot.
The difficulty I faced was that I could not tell how hard I had to swim in order to make progress against the current. I had to swim fast enough to beat it, but not so fast I ran out of strength before I reached the shore.
At the same time I had to keep twisting round to check the waves behind me. If I had been swamped unawares, and came up choking, I feared that would knock the last of the puff out of me and leave me at the mercy of the current. I swam partly on my front and partly on my back.
The panic began to rise again. In Britain, 435 people drowned in 2005, many because they misjudged their swimming ability, though these were mainly children. Here was I, an adult, and I had badly misjudged mine.
I kept going. It flashed through my mind that, as it wasn't cold, if I could just keep swimming I might be rescued. But that was ridiculous. Who was going to rescue me?
Then, suddenly, the shore was drawing closer. I was tiring and as I neared the shallows I again feared being turned over by the breaking waves and swept out. Finally, my feet touched the bottom and I struggled up the beach. My arms felt useless, like rubber.
Reader, do not do what I did. Panic kills. Never swim alone.