Which of the following is a sign of overloading a boat?

Overloading a boat can lead to serious safety hazards, and one clear sign of this condition is when the boat is swamped or takes on water. When a boat carries more weight than it is designed to handle, it decreases its buoyancy. This can result in the boat sitting lower in the water than normal, making it more susceptible to waves and adverse conditions, ultimately causing it to take on water. In extreme cases, this can lead to capsizing or sinking.

The other options do not indicate overloading. For instance, if a boat is traveling unusually fast, it can indicate other factors such as powerful engines or a lighter load, but not necessarily that it is overloaded. Operating silently might suggest efficient operation or a lack of power, which is unrelated to weight capacity. Finally, a boat having an even keel is a sign of proper loading and balance, countering the idea that it is overloaded. Recognizing the signs of overloading is crucial for ensuring safety on the water.