Why do you swim in cold water? Do you really do it every day? Doesn’t it give you a shock? Isn’t it dangerous?

You may as well ask me, Why do you write? And people have done this. They have also said, You must have to be very disciplined – do you really do it every day? And: Isn’t it hard?

Neither swimming in cold water nor writing come easily. Both require a certain amount of discipline; if you give up regular practice you lose your edge. This is true for many things in life. I know from bitter experience, having played musical instruments every day for years until I was pretty good, then once working life intruded, letting the daily practice slip, and finding that, years later, I was not so very good at playing any more.

Yes, I get a shock when I plunge into cold water. I am acclimatised now to the point that I can stay in for a lot longer than I used to and I don’t get the chills afterwards, but that doesn’t diminish the sharp seize that grips my heart when I lower myself in. And, yes, there are days when I get to the water’s edge thinking, ‘I am too tired today/too cold/not in the mood.’ Just as there are days when I look at a blank page and think, ‘I have nothing to say/don’t know what to write/am too tired/too cold/not in the mood.’

Yesterday I ran down to the cove and heard the sea’s loud whispers long before I could see its peaks and troughs. I told myself that a swim would not be on the cards today, and that in any case I didn’t feel like it. I had slept badly and was feeling melancholy, yet I kept on following the path, telling myself I would ‘just sit and look’. I pushed through the blackthorn and gorse and saw that, yes, the sea was choppy and, yes, the sky was dark grey and threatening rain. But there was not so much of a swell and the rain wasn’t likely to fall right overhead for a good ten minutes or more. Before I could talk myself out of it, I was throwing off my clothes, pulling my costume from my bag and heading to the edge of the rocks.

The cold made me shout and I paddled furiously towards my destination – a large rock about 25 metres away that my kids call Island Tosh. Once there, I was already grasped by the tingling sensation that is the addiction I crave, and the journey back to shore was blissful. I had stopped shouting and was swimming at a normal pace, enjoying the dark green glass of the water sliding over my hands, the feeling of warmth moving through my core, the mixture of greys and blues swirling in the sky overhead. I swam back out to Tosh one more time, grinning like an idiot, feeling the push and the pull of the sea as it played with me, making it harder to swim the closer I got to Tosh, but giving me a gentle shove back to the rocks as I turned around for the last time.

I pushed myself up and out, buzzing, talking to myself about how it felt to have swum a hundred metres in the sea in the second week in December. My dog watched me from a distance, disapproval written loud on her soft, loyal face. Why do you do this? she was asking, as so many people do.

The answer is the same as the reason I return to the page every day, however I am feeling: because I have to, because there is no other way to feel that I am truly alive. Writing, like swimming, is my own personal factory reset. The minute I plunge in – be it into cold water or a fresh new page – I am switching myself off and on again. Music used to do this to me. As a teen, if I were in a filthy hormonal mood I would run to the piano. An hour or so of crashing chords and tumbling scales and arpeggios, and I would re-emerge; washed clean, purified, my anger lost somewhere in those black and white keys.

Now it is the black and white of the words on the page. Or the black, blue and grey of the sea. The two things are so intertwined that I can hardly see the seams. When I am swimming, I am writing in my head. And often, like today, when I am writing, I am swimming in my head too.

Taking the plunge sometimes brings a shock, yes, but it always brings rewards.