What should happen when the stern is clear while maneuvering a boat?

When the stern is clear while maneuvering a boat, casting off the bow line is the correct action to take. This allows for increased maneuverability and helps facilitate the boat’s movement away from the dock or the area it's currently situated in. By freeing the bow line, the operator can effectively steer the boat as needed, without being hampered by a fixed connection at the front.

Dropping anchor, turning off the engine, or ensuring all crew members are seated may not directly support the goal of maneuverability during this phase. While these actions could have their places in other scenarios, they do not directly relate to optimizing the boat's movement once the stern is clear. Therefore, casting off the bow line promotes safety and effective navigation in open waters.