What is a critical feature of ECDIS regarding shoal waters?

The critical feature of ECDIS (Electronic Chart Display and Information System) in relation to shoal waters is its ability to generate alarms when a vessel approaches these shallow areas. This function is essential for ensuring navigational safety, as it alerts the navigator to potential grounding risks in waters that are too shallow for safe navigation.

ECDIS utilizes electronic charts and integrates information from various navigational sources, providing updated details about the water depth and the contours of the seabed. When a ship enters a designated safety zone near shoal water—often set based on the vessel's draft—the system triggers an alarm, prompting the crew to take necessary action to avoid entering dangerous territories. This proactive measure is crucial for preventing accidents and maintaining navigational safety in coastal and shallow regions.

The other options do not describe the primary safety feature associated with navigating shoal waters using ECDIS. For instance, the system does not inherently detect shallow areas on its own without prior input of relevant bathymetric data nor does it enhance radar visibility or operate without user input, both of which are functionalities not specifically related to addressing the challenges of navigating in close proximity to shoal waters.