Afterdrop & the subtle art of warming up

How to cope with afterdrop and the best way to warm up safely

Annie Spratt

“Afterdrop” is common after swimming in cold water; you get out and feel fine, and then you start to get colder, sometimes growing faint, shivering violently and feeling unwell.

Afterdrop happens because when you swim, your body shuts down circulation to your skin, pooling warm blood in your core. This process helps you stay in the water longer: with reduced circulation to your peripheries skin and sub-cutaneous fat is turned into a thermal layer, similar to a natural wetsuit – hence the wild swimmers’ term bioprene for fat.

But as you start to warm up, this process reverses: blood starts to recirculate in your extremities and peripheral blood vessels, cooling as it travels. You can lose up to 4.5°C from your core temperature (according to Golden and Tipton, Essentials of Sea Survival), bringing on shivering, hypothermia, or feeling faint and unwell.

The key to warming up and staying well is to warm up slowly and gradually. If you attempt to rush it by, for example, having a warm shower or bath, you will draw the warm blood that has pooled in your core to the skin at speed, leading to rapid cooling. You will quite likely faint as your temperature plummets along with your blood pressure.


Annie Spratt
Alex Holt
Llyn Cowlyd ©Vivienne Rickman-Poole

How to warm up

  • To minimise the risk of afterdrop, dress immediately starting with the top half of your body. Put on a hat and gloves and have a warm (non-alcoholic) drink.
  • Dry yourself off ASAP – remove all wet layers
  • Don layers of warm clothing including a woolly hat and gloves. Silver foil blankets do not help swimmers – unlike runners, for example, swimmers are not radiating heat post swim, so there is no escaping heat for the silver foil blanket to trap.
  • Sip a warm drink: this helps warm the body gently from the inside.
  • Eat something: sugar will help raise body temperature.
  • Sit in a warm environment: in the absence of more salubrious spaces, cars, with heaters on full, are popular with channel swimmers.
  • If you feel okay, walk around to generate body heat. It can take some time to warm properly.
  • If you feel unwell at this stage, sit down somewhere warm.


With help from Dr Mark Harper and Heather Massey from the Extreme Environments Laboratory at the University of Portsmouth