Conscious that this writing lark is not very conducive to maintaining a decent level of fitness, I recently started swimming again. Now I don’t have a pool of my own, so when I was invited to join some friends in their time-share slot at a local private establishment, I jumped at the chance to use a pool that I didn’t have to share with the world and his wife (and their children). Even better, the next week none of my friends could go, so I went on my own.

Brilliant, I thought. I’ll have the pool to myself; I’ll get that all-important exercise, and I’ll be able to devote some serious thinking time to the development of my new novel, unhindered. That’s the good thing about swimming: the very mindlessness of ploughing up and down frees your brain to wander.  You can concentrate on nothing but the number of lengths you’ve covered, but if you’re a true daydreamer, you can use the time much more effectively.

Or that’s what I thought. Swimming alone turned out to be a very spooky experience indeed.

A clutch of pink and silver balloons floated close to the ceiling, reminders of a long-finished birthday party. The water, like the ambient temperature in the pool room, was blood heat. It was like swimming in a womb. The constantly changing overhead lighting cast eerie shadows on the still water, creating sea monsters beneath me. The water booming in the filtration system echoed eerily around the empty space. The very empty space. I could drown here, I thought, and no one would know. Well, not until the next time-sharers arrived in an hour. But still.

I scanned the ceiling for cameras – maybe I was being watched – and plunged on.

Gradually, as I continued to swim, accompanied by an unshakeable feeling of being pursued by a woman-eating fish hoping to drag me into the watery depths, the germ of an idea took hold. It continued to grow until it pushed my anxiety to one side and by the end of the session I had the bare bones of a thrilling story. Obviously it contained all the elements I had been anxious about: the hint of menace, the suspicion of being watched, the complete isolation, the threat of something indefinable. The location was perfect for a murder – who would ever know what happened?

At the end of the session I hurried to make some notes on my phone (that’s the only problem with swimming for stimulation with a memory like mine – I forget.) But the details were so vivid there was no danger of that. My imagination was in overdrive. I had enough material for several stories. By the time I’d driven home the first one was all but written in my head.

So my advice would be to take your inspiration wherever you find it – improved fitness isn’t the only benefit of exercise. But maybe stick to public pools; there’s less chance of your imagination being hijacked!