How do 'end devices' affect visibility according to COLREGs?

End devices, which include lights, shapes, and sound signals on vessels, play a critical role in ensuring safety at sea by enhancing visibility under various conditions. The correct answer highlights the necessity for these devices to be properly fitted and maintained to ensure that vessels remain visible regardless of the environmental circumstances they face, such as varying visibility due to weather changes, darkness, or other obstructions.

This requirement is rooted in the COLREGs, which mandate that vessels must be identifiable to other vessels to prevent collisions. Proper maintenance and use of end devices are essential, as they are crucial for communicating a vessel's presence, type, and operational status, particularly during conditions that impair visibility.

The option suggesting that end devices are optional and can be ignored if conditions are good neglects the fundamental safety principles outlined in the COLREGs. Likewise, the idea that such devices only need to function in heavy fog undermines the regulations, which apply in a broad range of circumstances. Furthermore, limiting the necessity of end devices to only large vessels is incorrect since all vessels, regardless of size, are required to exhibit appropriate signals for safety on the water.