Final answer:
Swimming during a thunderstorm is dangerous because our bodies and impure water are good conductors of electricity, potentially causing harm when lightning strikes.
Step-by-step explanation:
Even though pure water isn't a good conductor of electricity, it's important to understand why swimming during a thunderstorm is dangerous. While pure water itself does not conduct electricity well, our bodies do because of the water within us, and because natural waters like lakes and pools usually contain impurities like salts that turn them into good conductors. When lightning strikes water, it can spread through the water and potentially harm anyone in it due to the lower resistance pathways through the human body compared to the surrounding water. Another reason for the danger is the Earth's role as an electron sink, attracting the current to people swimming, who may inadvertently become a direct path for the electricity.