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A method based on repeated freediving was developed to rescue subjects trapped in cars underwater – a scenario leading to 5–6 annual deaths in Sweden, and thousands globally. We determined rescue time and whether the divers were at risk of hypoxic blackout. Cars containing 5 kg negatively buoyant rescue-dummies strapped with seatbelts were placed on 5 m and 8 m depth. Eight freediving-instructors made 230 freedives, working in pairs with one diver always at the surface. For each rescue, two freedivers, equipped with mask, snorkel, fins, weight-belt, wetsuit and a buoy with belt-cutter and glass-breaker freedived alternating in turns between the divers. They accomplished a maximum of one of the following tasks per dive; (1) Finding the car; (2) Marking car with buoy; (3) Opening door/crushing window. (4) Opening/cutting belt; (5) Retrieving dummy to surface; (6) Transporting dummy to shore. Dummies were retrieved to shore from 5 m depth within a mean (SD) duration of 4 min 16 s (1 min 36 s) and from 8 m within 6 min 22 s (2 min 13 s; P < 0.05). Mean dive duration was 28(7)s (14–46 s), with 3 dives over 40 s duration. Freedivers arterial oxygen saturation (SaO2) levels were measured in dives of 30, 35, 40 and 45 s using pulse oximetry. Mean (SD) SaO 2 at 20 s after surfacing was 90% for 45 s dives. This allows rapid recovery and gives a safety margin to the 50% SaO2 level when divers may risk blackout. We concluded that repeated freediving is efficient for rescuing victims trapped in cars underwater within their survival time, and following recommended methods and dive durations, rescue divers are not exposed to risk. [ABSTRACT FROM AUTHOR]