## 1 Introduction  
Psychological responses to cold exposure may influence athletic performance and can be critical in extreme environmental conditions. According to psychologist [PERSON], understanding the psychological mechanisms of the cold response is the first step toward adaptation [1]. The sudden mental stress of entering icy water releases a number of phenomena in the body [2].  
Noradrenaline, along with adrenaline, thyroid hormones, and adrenal cortical steroids, plays a significant role in cold adaptation. These agents increase energy production. Tolerance to cold results in higher sensitivity to noradrenaline and in raised capacity to generate adrenaline and noradrenaline. Nevertheless, cold-tolerant individuals usually exhibit suppressed rates of resting sympathetic nervous system arousal, unlike those who are not cold-tolerant or trained [3].  
Winter swimming has been shown to exert a positive effect on the human psyche [4, 5, 6, 7] and to bring about antidepressant effects [8]. Regular winter swimming leads to an improvement in the overall well-being of those suffering from rheumatism, fibromyalgia, or asthma [4]. There is a well-known case report of a 24-year-old woman with symptoms of severe depression and anxiety [8]. Individuals who perceive themselves as tolerating hot and cold experience stable emotions, as well as greater activity and vigor [3]. Habituation or acclimatization is considered to be the mechanism of adaptation [9].  
This is, however, related to quick changes in cardiac autonomic balance, characterized by significant vagal tone withdrawal. Caution is thus recommended, especially when a high cardiac risk exists. Moreover, the cold shock response should be reduced with the use of suitable strategies [10]. From a psychological perspective, examples of such strategies might include adopting an appropriate attitude toward the stimuli that one is about to experience, such as preparing for the appearance of cold, cramps, etc. (becoming comfortable with what lies ahead), or breathing exercises. These techniques help reduce the psychological shock that can occur during a sudden change in temperature. As for the physiological risk, a head bath with cold water is applied in turn.  
Immersion in cold water is always accompanied by a significant risk. Cold shock can lead to death caused by cardiac arrhythmia or water inhalation [11]. In 2021, six deaths were reported in English rivers or lakes during a summer weekend [12]. Those who wish to practise cold-water immersion should take some simple protective means: (1) enter the water slowly and in a controlled way in order to inhibit the effect of cold shock; (2) splash water onto the whole body before the immersion; (3) move slowly into the water; (4) avoid progressing further into the water until breathing is under control; (5) start practising immersions in the summer, when the water temperature is higher; (6) seek a physician's advice on underlying health conditions that might increase the risk, e.g., high blood pressure or heart disease; (7) follow information on cold water immersion for the unexperienced, e.g., on the Outdoor Swimming Society website [7].  
The present study aimed to determine if regular winter swimmers differed from those who did not practise winter swimming in terms of (1) daily perceived emotional states, (2) subjectively perceived satisfaction with life, and (3) hormone concentrations. An additional objective was to investigate how a single immersion in cold water in regular winter swimmers affected their subjectively assessed emotional states and levels of stress hormones.