When the body hits cold water, vessels constrict, heart rate climbs, and noradrenaline floods the system. The result is a powerful natural anti-inflammatory and a nervous-system reset that leaves you alert, calm, and clear-headed.

Two to five minutes for a healthy adult. Vessels tighten, blood rushes inward, the chemical cascade begins. This is where the work happens — and where the mind learns it can do harder things than it thought.