Whether in lake, lido, river or sea, we know the benefits of swimming outdoors and in nature - environmentally friendly and accessible, it can influence our happiness, our energy and our inner tranquility, and give us that winter glow. Danish scientist Dr Susanna Soberg leads us step by step into the icy water and explains the 'cold-shock response', the massive endorphin rush as our body reacts and adapts to very cold temperatures through the winter season. Not only do our circulation, heart, lungs and skin respond positively, but our immune system, metabolism and mental health too. In particular she explains how our 'brown fat' is activated to benefit multiple health conditions.