Even as a practitioner, I have experienced the frustration of working hard in cold water only to feel heavier the next day. From a Western medical perspective, the body may treat subcutaneous fat as a protective insulation layer in cold environments, making it more resistant to being burned. In Traditional Korean Medicine, we analyze this through the concept of 'Susup' (water-dampness). Those with a 'Biheo' (Spleen deficiency) constitution often lack the 'transportation and transformation' power to expel moisture effectively. Frequent contact with cold water can block the circulation of Qi and Blood, resulting in 'Eohyeol' (blood stasis) or 'Dameum' (sticky metabolic waste). If you find your hands and feet are particularly cold or your digestion is sluggish after swimming, it means your internal 'Fire' (metabolic heat) is being overwhelmed by the external 'Water' energy. Rather than just increasing exercise intensity, the key to successful weight loss in this case is to first clear the internal coldness and restore healthy circulation.