When you suddenly fall into very cold water, your body can have a big reaction called a "cold shock response." This happens because the cold water makes you want to breathe in fast. If you breathe in water, you can drown. Falling into cold water can make your heart work too hard, especially if your heart is not very strong. This can cause big problems like a heart attack. Very cold water can also make your body very cold and cause other heart problems. Some people die because their heart and breathing don't work right in cold water. But some persons like to swim in very cold water. They do this as a sport and say it's good for them if they do it a lot. When you go into cold water, your body can go through different steps. Each step has its own risks. This is called "Cold Water Immersion Syndrome."

Some people like to swim in the winter. They swim outside in cold water or in pools without heat. In very cold places, the water can turn to ice. People have to make a hole in the ice to swim. Swimming in the cold is a special thing people do in places like Scandinavia and Eastern Europe. It can be part of a church holiday called Epiphany. There are swimming races in the cold water too. Swimmers wear only normal bathing suits, no special warm clothes. There are famous swimmers who like the ice, like Lynne Cox and Lewis Gordon Pugh. In North America and Europe, people jump into cold water to start the New Year. They do not swim for long. There are big races in cold water around the world. There are rules for these races. The water is very cold, and swimmers wear only goggles, a bathing suit, and a swim cap. To stop ice from covering the swim area, people use a pump or cover the hole. They also have a warm path to walk from changing rooms to the ice.

Some people get red, itchy spots on their skin when they are cold. These spots are called hives. They can get bigger. Hives can appear on the hands and feet too. There are two main kinds of this skin problem. One kind you can get from your family. The other kind starts when you are young or a grown-up. It can be dangerous because it can make it hard to breathe if you eat or drink something cold. It can also be very bad if you swim in cold water. There are different types of this skin problem: One type happens when you touch something cold. This can be when it's rainy or windy, or when swimming in cold water. Another rare type can come from problems in your blood. It can make your hands and feet change color or hurt. A third type happens when your whole body gets cold. Then your whole body can get hives. The type that you can get from your family gives you a rash and can make you feel very cold with fever. It starts if it is colder than a warm day.