Living next to the sea, I used to frequently go for late night swims, despite the 10 degree, pitch black water, concealed rocks and kelp forests. Swimming in the dark ocean under the stars, it’s hard not to feel alive and at peace out in something that seemed so scary from the shore, and continue feeling incredible for a few hours after.
I think there are two effects at play. Such a sheer, sensory experience of nature is bound to have an effect. But there’s a lot of talk on the positive effects of cold water. When learning to freedive, a friend taught me about the mammalian diving instinct. She mentioned that it stems from the basic fact that we evolved to be more acquainted to aquatic environments. When freediving you’d splash your face with cold water, triggering a physiological response preparing our body for diving. See her talk
Cold showers also seem to have a great effect. It could be the will strengthening from the “uncomfortable” act or the vasoconstriction and subsequent dilation bringing fresh blood to different parts of your body. It could be the increase in Adiponectin regulating blood glucose levels, or the mammalian dive reflex causing fresh oxygenated blood to be released from your spleen into your bloodstream. But I like to think it’s a reminder of the ancestral ties we had to the ocean.
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