Why is placing an unresponsive person on their back over a rescue tube an effective method for giving rescue breaths in water?

Placing an unresponsive person on their back over a rescue tube is effective for giving rescue breaths in water primarily because the flotation device helps keep the individual at the surface while simultaneously opening the airway. When a person is positioned on their back, the buoyancy of the rescue tube supports their body, preventing the head from submerging and ensuring that the airway remains clear and unobstructed. This position promotes proper ventilation and allows for effective rescue breaths without the risk of the person's face being immersed in water, which could lead to complications such as water entering the lungs.

This method also enhances the rescuer’s ability to deliver breaths efficiently while maintaining control over the airway. Ensuring that the person is at the surface is crucial as it minimizes the risk of drowning and maximizes the chances of successful reoxygenation of their blood, which is vital in an emergency situation where time is critical.