Which of the following is considered a sign of distress while boating?

Waving arms aggressively is indeed a recognized sign of distress while boating. This behavior is a clear signal to others that help is needed, as it typically indicates that someone is in trouble or is unable to manage a situation effectively. It is a visible and noticeable action that can attract the attention of other boaters or rescue personnel nearby.

In contrast, flashing lights can indicate a variety of scenarios, including operational signals or communicating with other boats, rather than specifically a distress signal. Turning off navigation lights is unsafe and could lead to misunderstandings on the water, and does not convey the urgency of a distress signal. Additionally, having all passengers sitting quietly does not suggest distress; in fact, it may indicate a calm situation onboard. Understanding the appropriate signals for distress can enhance safety and communication while boating, making it crucial for boaters to be able to recognize and respond to such signs effectively.