Swimming is a popular sport in the United Kingdom (UK); however, cold water immersion often found in open waters in the UK is not without increased risk. Drowning is among the leading cause of accidental death in 1-14 year-olds in most countries. We examined whether children and adults exhibit similar cold shock responses; their rate of cooling while swimming; and subjective recognition of cooling. Nineteen children aged 10-11 years voluntarily undertook a 5 min static immersion in 15 °C (59 °F) water. Ten of them then completed a swim of up to 40 min. Resting heart rate, respiratory frequency and inspiratory volume increased in all participants on initial immersion. The mean (+SD) cooling rate while swimming was 2.5 °C hr1 (+3.1)). No significant correlation was found between cooling rate and thermal sensation or comfort, implying a lack of subjective awareness in children. On comparing data from unacclimatized adults in 12°C (53.6 °F) water, children showed a smaller ‘cold shock’ response (p < .05), and no difference was found in cooling rates during swimming.