What to Expect When Entering Cold Water

cold water immersion swimmer with green cap

During cold water immersion, several responses take place within your body. Learning how to cope with cold water and knowing your limitations is key to staying safe during open water swimming.

The initial cold-shock response

The cold-shock response lasts for only a few minutes after entering cold water, and refers to the effect of the cold on your breathing.

Initially, there is an automatic gasp reflex in response to rapid skin cooling. Breathing rate and heart rate also tend to increase. The cold-shock response can be controlled by remaining calm and controlling your breathing.

How your body adapts to cold water immersion

Your body is built to maintain a deep body temperature between 36.5 – 37.5°C, a process known as thermoregulation. This is primarily controlled by an area in the brain called the hypothalamus, which initiates a variety of responses to temperature fluctuations.

When the body is too cool, body heat is preserved. Vasoconstriction narrows blood vessels to decrease blood flow to the extremities (hands and feet), hereby decreasing heat loss to vital organs such as the heart and lungs. You may feel your fingers and toes starting to get cold or even slightly numb.

If exposed to the cold for too long, the body loses it’s ability to maintain a stable deep body temperate, and gradually starts to lose body heat. However, your body adapts to frequent cold exposures, and it gets easier to handle every time you get in.

Cold water immersion entry tips:

  • Slow immersion. Enter the water slowly so that your body can adapt to the change in temperature. It is not advised to dive into very cold water, especially if you are not experienced in cold water swimming. 
  • Control your breathing. As you enter cold water, focus on slowing and controlling your breathing, especially when submerging your face. Remember that the cold-shock response will only last a few minutes before your body settles into the cold.
  • Remain calm and relaxed. As you start swimming, remain calm and relaxed. Focus on lengthening your stroke and relaxing your muscles. Start off swimming at an easy pace, and once you feel comfortable, you can start increasing your pace.

Always swim with a buddy or in a group, as safety is the number one priority when it comes to cold water.

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