This report describes the case of an 18-year-old woman who was found in the sea suffering from cardiac arrest and hypothermia, 90 minutes after she entered the water to swim. The rescue team used an automated external defibrillator to record prehospital management. This recording showed an isoelectric electrocardiogram followed by a ventricular fibrillation, an unsuccessful defibrillation, and lastly, a return of spontaneous circulation with Osborn wave. When she was admitted to the intensive care unit two hours later, the woman's central temperature was 28°C. The case is interesting because of several points. First, to the best of the authors' knowledge, this is the only case of cardiac arrest with severe hypothermia followed by a return of spontaneous circulation documented with an automated external defibrillator recording. Second, the hypothermia is an atypical case occurring in the summer. Hypothermia must be considered even in unlikely circumstances, such as summer in the south of France, when ambient temperatures are high. Lastly, after three days, the patient recovered successfully from cardiopulmonary arrest without cerebral dysfunction.