Why cold water shock catches even strong swimmers

Britain's seas are cold. Even in a warm August, the water around our coast often sits between 14°C and 17°C, and in winter it can drop to 4°C or lower. That is cold enough to trigger a violent physiological response the moment you enter the water. It is not about being tough or experienced. Cold water shock affects everyone.

The first thing that happens is a gasp reflex. You involuntarily suck in air, and if your head is underwater, you can inhale water. Your heart rate and blood pressure spike. You begin to hyperventilate, breathing four or five times faster than normal. Panic sets in. This is the stage when most drownings happen, often within the first minute.

Float first: the single most important action

Your instinct will tell you to swim. Fight it. Swimming immediately increases your heart rate, makes you gasp harder, and pushes cold blood from your limbs back to your core. That can lead to a further drop in core temperature and, in some cases, cardiac arrest. Instead, float first.

Roll onto your back. Spread your arms and legs wide, like a starfish. Keep your head back, ears in the water, and your airway clear. Move as little as possible. If you have a lifejacket, it will keep you afloat, but you still need to adopt this position. If you do not, floating on your back is far easier than treading water. The goal is to survive the first 60 seconds without inhaling water.

Control your breathing: the 60-second rule

Once you are floating, focus entirely on your breath. The gasp reflex and hyperventilation will pass in about 30 to 60 seconds if you do not fight them. Breathe in slowly through your nose, then out through pursed lips, as if you are blowing out a candle. Count to four on the inhale, hold for two, and count to six on the exhale. This is not the time for deep, panicked breaths. Slow, controlled breathing tells your nervous system that you are not in immediate danger.

Only once your breathing is under control should you think about what to do next. That usually takes less than a minute, but it feels like an eternity. Trust the process. Breathe first, swim later.

Call for help: how to signal and who to contact

As soon as you can speak, call for help. If you are near a beach or harbour, shout and wave one arm in a slow arc. If you have a whistle attached to your lifejacket, use it. Three blasts is the international distress signal. If you have a mobile phone in a waterproof pouch, dial 999 or 112 and ask for the coastguard. Keep the phone dry and hold it clear of the water.

If you are on a boat that has capsized or you have fallen overboard, try to stay with the vessel. It is much easier for rescuers to spot a boat than a head in the water. If the boat has a VHF radio, use channel 16. Press the red DSC distress button if you can reach it. If you cannot speak, press the button and wait. The coastguard will have your position and will send help.

If you cannot call for help: conserve heat and stay visible

If there is no phone, no radio, and no one within earshot, your priority shifts to survival and rescue. Adopt the HELP position: Heat Escape Lessening Posture. Pull your knees up to your chest, cross your arms over your lifejacket, and hug yourself. This protects your core. If you are with others, huddle together in a tight circle, facing inwards. This shares warmth and makes you a bigger target for rescuers.

Do not swim unless the shore is very close and you are certain you can make it. Swimming increases heat loss by up to 35 per cent compared with staying still. It also moves cold blood from your limbs to your heart. If you must swim, do it on your back with a slow, steady stroke, keeping your head above water. But for most people in cold UK seas, staying still and waiting for rescue is the safer choice.

The rescuer's rule: reach, throw, don't go

If you see someone in trouble in cold water, do not jump in after them. Cold water shock can disable you just as quickly. Instead, call for help immediately. Then use the reach and throw principle. Reach with a pole, a branch, or a paddle. Throw a lifebuoy, a float, or an empty water container tied to a rope. If you must enter the water, wear a lifejacket, take a flotation device, and only do so as a last resort.

The person in the water should float first and control their breathing. You, the rescuer, should stay safe and get professional help on the way. That is how cold water shock is survived. It is not about swimming harder. It is about doing the right thing first.