The sky hook used to rescue Bond at the end of the film was a rescue system used by the United States military at the time. At "Thunderball"'s release, there was confusion as to whether a rebreather such as the one that appears in the film existed; most Bond gadgets, while implausible, often are based upon real technology. In the real world, a rebreather could not be so small, as it has no room for the breathing bag, while the alternative open-circuit scuba releases exhalation bubbles, which the film device does not. It was made with two CO2 bottles glued together and painted, with a small mouthpiece attached. For this reason, when the Royal Corps of Engineers asked Peter Lamont how long a man could use the device underwater, the answer was "As long as you can hold your breath."