Marine Survival in the Mediterranean: A Pilot Study on the Cognitive and Cardiorespiratory Response to Sudden Cool Water Immersion.
Level 2 - randomized trial
Randomized crossover trial in human subjects
PubMed 35162622 · doi:10.3390/ijerph19031601
What was done
Ten active, healthy men participated in a randomized crossover study comparing a thermoneutral dry control environment (~25 °C room air) to sudden neck-deep cool water immersion (~18 °C), separated by at least 7 days. Cognitive function was measured with the Symbol Digit Modalities Test across six 45-second blocks with 5-second intervals. Continuously recorded physiological measures included heart rate, minute ventilation, oxygen consumption, and respiratory frequency.
What was found
During the initial response to cool water immersion (<2 min) compared to control: - Symbol Digit Modalities Test performance decreased by ~11% (p = 0.025). - Oxygen consumption was 149% higher (CI: 5.1 to 9.1 L/min, p < 0.0001). - Heart rate was elevated (CI: 13 to 38 beats per minute, p = 0.001).
Why it matters
Even moderately cool water typical of Mediterranean Sea temperatures triggers acute cold-shock responses and cognitive impairment within the first two minutes, which may jeopardize survival decisions during maritime accidents.
Limits
The study is limited by a very small sample size (n = 10) consisting solely of healthy, active men, preventing generalization to diverse migrant populations including women, children, and individuals with medical conditions. Laboratory immersion does not replicate open-sea survival stressors such as waves, panic, clothing drag, or prolonged exposure.