Mid-competition deaths of triathletes during the swimming event are increasing and the cause of these deaths has not been fully elucidated. One hypothesis is that a conflict of autonomic signals [1] caused by the parasympathetic dive response and sympathetic cold shock response trigger cardiac events that lead to death. The aim was to investigate the effects of cold water face immersion on heart rate variability (HRV) in healthy subjects. This study was conducted using previously collected data. 39 healthy subjects (26 male) underwent 5 consecutive one-minute HRV measurements. The study was given ethical approval by the Research Ethics committee. All participating subjects gave informed and signed consent. HRV was recorded using an electrocardiogram. LabChart software and a PowerLab were used for data acquisition. The order of the experiments was: control 1, 26 Celsius water face immersion, control 2, 11 Celsius water face immersion and control 3. Each experiment was analysed in 6 x 10 second time bins (0-10, 10-20, 20-30, 30-40, 40-50 and 50-60 seconds). Data was also normalised by taking into account the heart rate [2].The results were analysed by repeated measures ANOVA. Subjects’ mean (± S.D.) age was 23.4 ± 7.1 years and mean BMI was 25.1 ± 5.2 kg m-2. Results showed a significant sympathetic response (increased heart rate) in both face immersion tests in the initial 20 seconds following immersion with bradycardia over the subsequent 40 seconds (P<0.001 for both tests). For 11 Celsius immersion there were also significant changes in both sympathetic (increased normalised low frequency P<0.01) and parasympathetic signalling (decreased normalised high frequency P<0.001) within the first 10 seconds of the face immersion test. The main findings indicate the first 10 seconds of the face immersion test could be a potential timeframe for autonomic conflict. The magnitude of changes in autonomic signalling were greater in the 26 Celsius water test, indicating that habituation may be occurring as this test was performed first. Further work is needed to investigate any effect of the order of tests and potentially any benefit of triathletes splashing their face with water before swimming, as a form of habituation, to possibly reduce any cardiac complications.