Under what conditions would a parallel approach be preferred?

A parallel approach is typically preferred under conditions where there is calm weather, a slow drift of the vessel, and ample time for passing gear. This approach allows for a controlled and gradual approach to the docking situation, minimizing the risks associated with external factors like wind and current. In calm weather, there are fewer disruptions that could compromise the maneuverability of the vessel. A slow drift provides additional time for careful navigation and assessment, enabling the crew to make necessary adjustments without the rush of adverse conditions. Having ample time for passing gear allows for better planning and execution of the maneuver, ensuring that all aspects of the vessels' approach are coordinated effectively.

In contrast, conditions such as heavy weather or strong tides can complicate an approach and may necessitate different strategies that account for increased risks and reduced maneuverability. Similarly, zero visibility would typically require different precautions, such as using radar and other navigational aids to ensure safety, rather than a parallel approach that relies on visual references. Thus, calm conditions with enough time for planning and execution make a parallel approach the safest and most effective choice for docking operations.