What is required of all ships when in restricted visibility according to Rule 19?

When operating in restricted visibility, Rule 19 of the International Regulations for Preventing Collisions at Sea (COLREGs) emphasizes the need for vessels to be prepared for immediate maneuvering. This includes having all engines on standby, which ensures that the vessel can react promptly to changing situations or obstacles that may arise in limited visibility conditions.

In restricted visibility, vessels face increased risk due to the inability to see other ships, navigational aids, or hazards; therefore, maintaining engines on standby allows for quicker responses and enhances overall safety. This readiness is crucial for avoiding collisions and ensuring that the vessel can navigate safely through uncertain waters or traffic scenarios.

Other considerations, such as speed or navigation channels, are relevant in different contexts, but the primary focus of Rule 19 is on maintaining a state of preparedness to maneuver effectively during such conditions.