Research shows that cold-water swimmers have fewer colds and lower rates of depression. In one study, people immersed in cold water for an hour three times a week showed an increase in white blood cells, which are linked with immunity. Czech researchers say cold water is a mild stressor and activates the immune system.
Cold-water swimming also burns extra calories as the body uses energy to keep warm. And it can boost feel-good hormones, as the “pain” of cold water results in an endorphin rush.