Outdoor Cold Water and Winter Swimming Safety: Information and advice for swimmers when planning trips to rivers, lakes, lidos and the sea:
Cold Shock (Sudden Immersion Syndrome)
Cold Shock can occur if you enter cold water too quickly. If your face is submerged suddenly in cold water it can cause an involuntary gasp which can then lead to hyperventilation, resulting in a lack of oxygen to the brain.
Always enter the water gradually, let the body settle before you start to swim. Avoid diving. Acclimatisation/habituation is very important but even if you are a hardened cold water swimmer, take care!
Hyperthermia
Hyperthermia is progressive drop in body temperature which can be very unpleasant, dangerous and potentially fatal. Know your limits and never swim alone in cold water. Listen to your own body. It takes a while for the body to chill but everyone is different and has a varying level of tolerance to cold. What is safe for one person may not be safe for another.
As hyperthermia takes hold, initially blood vessels constrict and blood pressure increases. A warning sign is a loss of feeling in your extremities and your hands forming a “claw”. At this point you should think about finishing your swim safely and quickly. You may notice a loss of strength in your limbs and a deterioration of motor control. Disorientation, loss of focus and mental impairment are sure signs that you have stayed in the water too long. Concentrate on warming up and ask for help.
After drop
After drop is a commonly used term for the dangerous impact of resumption of blood circulation. It can happen after a cold swim if you warm up too suddenly. Cooled surface blood starts to return to the body’s core and the resulting drop in core temperature can be dangerous. Hot showers and vigorous exercise can accelerate the process by supressing the shiver response, encouraging dangerous early resumption of the circulation and increasing the after drop. This can make your blood pressure drop as the blood flow increases. You may feel faint, light-headed, and possibly collapse. Shivering is good. It is the body’s way of warming itself. The best thing to do is warm up slowly: put on layers, and take sips of warm drinks
When swimming you must drink absolutely NO alcohol as it interferes with the body’s ability to control blood flow and regulate temperature.
Preparation
Be realistic and know your limits. Make sure you have warm layers which are easy to pull on. Lay your clothes out in the order that you will be putting them back on. Have a warm hat, warm drinks and some sugary food. Please take particular care if you have any heart conditions or blood pressure issues. If there are lifeguards speak to them about any medical conditions. If in doubt speak to your GP.