Adaptation to cold water immersion leads to less vigorous shivering, potentially due to increased mitochondrial density in muscle cells enhancing thermogenesis.

“if you also get adapted to the cold water you will have less shivering they would be less vigorous they will be very small so you wouldn't probably know that you shivering because it's the Shivering is so small and the mitochondria in the muscle cells will be so densed that it doesn't need to shiver maybe that much to get that thermogenesis going”