What does Rule 19 emphasize regarding vessels in restricted visibility?

Rule 19 of the International Regulations for Preventing Collisions at Sea (COLREGs) addresses the responsibilities of vessels when navigating in restricted visibility, such as fog or heavy rain. The rule emphasizes that vessels must proceed with caution and at a safe speed to avoid collisions. This means that they should take extra care to be aware of their surroundings and maintain a speed that allows them enough time to react appropriately if they detect other vessels or obstacles.

By highlighting the need for caution and safe speed, Rule 19 acknowledges the challenges inherent in navigation during periods of limited visibility and encourages mariners to prioritize safety over speed and maneuverability. Consequently, vessels are required to be prepared to stop within a distance appropriate to the prevailing conditions and to implement measures such as using sound signals to communicate their presence to others.

Engaging in aggressive approaches, moving at full throttle, or following closely behind other vessels, as mentioned in the other options, do not align with the principle of ensuring safety during restricted visibility situations. Such actions could increase the risk of accidents, which is why Rule 19 specifically advises caution and proper speed management as critical for safe navigation under these circumstances.