What is a key characteristic of a narrow channel?

A narrow channel is often characterized by limitations related to depth and proximity to hazards, making option B the correct choice. This is crucial for navigators as these conditions can significantly impact the safety of passage. Shallow areas can pose grounding risks for vessels, while nearby hazards, such as rocks or obstructive structures, require careful navigation to avoid collisions.

In contrast, the other options do not accurately capture the complexities associated with navigating narrow channels. While some narrow channels may be marked, it is not guaranteed that they are always well-marked, as marking depends on various factors such as local regulations and geography. The notion that narrow channels allow for free maneuvering is misleading because the very nature of being "narrow" implies restricted space, which can complicate navigation. Moreover, a narrow channel is rarely straight and wide; such characteristics would not define a channel that is fundamentally narrow. Understanding these characteristics is essential for safe navigation in challenging waterways.