According to lightning safety recommendations, what is the correct action to take after hearing thunder?

When thunder is heard, it's critical to adhere to safety protocols because it signifies that lightning is nearby. The correct action is to wait 30 minutes after the last sound of thunder before resuming activities. This recommendation is grounded in the understanding that lightning can strike several miles away from a storm, and the presence of thunder indicates the potential for lightning strikes.

The 30-minute rule allows for the storm to pass and provides an additional safety buffer. This waiting period is based on observations that clear conditions may follow an initial thunderclap, but lingering electrical activity can still pose a danger. Therefore, it's essential to ensure that the environment is considered safe before returning to any outdoor activity, particularly swim-related activities, which can be especially dangerous during thunderstorms.

Moving on to other options, resuming activities immediately disregards the risks posed by nearby lightning and fails to adhere to safety recommendations. Waiting 15 minutes after the last sound of thunder is insufficient, as conditions may still not be safe. Lastly, only leaving the water if there’s visible lightning also presents a hazard since the presence of thunder indicates that lightning could strike even if you don't see it. Thus, the 30-minute waiting period following the last thunder sound is the most prudent and safest action to take.