What should vessels regularly do to ensure safety when navigating in crowded waters?

Answer: C — maintain a vigilant look-out

Maintaining a vigilant lookout is crucial for ensuring safety when navigating in crowded waters. This practice helps to identify other vessels, navigational hazards, and changes in the environment that could pose a risk to safe navigation. In crowded areas, where the density of vessels is high, being attentive to what is occurring around you can prevent collisions and enhance overall situational awareness. A vigilant lookout allows for timely adjustments in course or speed in response to developing situations, ensuring a proactive approach to safety. While relying on radio communications can be an important tool in navigation, it should not be the sole method of awareness, especially in busy waterways where visual contact is vital. Checking navigation lights is also important for visibility and compliance with regulations, but this action alone does not address the necessity for ongoing awareness of surrounding vessels and conditions. Staying anchored would limit maneuverability and response to changing situations, which is counterproductive in crowded waters where movement is often required to maintain safety.