The best way to prepare is to “swim down the temperatures” throughout autumn. But you can acclimatise at any point; start with just one minute twice a week and build up. You can also prepare your body with very cold, short showers.

Plan your swim carefully. Always go with someone else, who stays on land. Agree how long you’re going to be in the water, and how you will get in and out. When you get in, aim to be immersed within three minutes, or you will just get too cold. Splash water on your chest (if you’re not in a wetsuit) and face. Always get out of the water at the agreed time – or sooner. The person swimming is not the best judge of when it’s time to get out (the cold can make you confused).

Recovery is key. Take flip-flops and leave them at the water’s edge to protect your feet from frozen ground. If you’re wearing a wetsuit, get it off quickly after your swim, towel off and start putting on lots of layers. I usually keep my swim hat on and add a woolly hat on top. Aim to be dressed within five minutes. Drink something warm and eat something sugary (I like parkin). Do not have a hot shower – your body will think it’s warm and will send blood away from your vital organs.

Enjoy the rush. It’s addictive, boosting mental strength and the immune system.

Over-breathe. Experienced winter swimmers take two breaths in instead of one, getting more oxygen to the blood.

• Matt Davenport is a competitive winter swimmer and a Selkie brand ambassador.