What can be a sign to return to shore quickly?

Thunder can be a significant indicator to return to shore quickly due to the potential for severe weather that typically accompanies it. Thunder signifies the presence of a thunderstorm, which can bring heavy rain, lightning, strong winds, and turbulent seas. These conditions can be dangerous for individuals engaged in activities on or near the water, such as boating or swimming.

In contrast, calm weather, clear skies, and warm water generally suggest safe and favorable conditions for outdoor activities. Calm weather and clear skies indicate stability and low risk of sudden weather changes, while warm water often denotes a pleasant swimming environment. Thus, while those conditions are typically inviting, thunder serves as a clear warning sign that immediate action should be taken for safety.