When a sailor is called "Captain," what does it indicate?

When a sailor is referred to as "Captain," it typically indicates their position as the commanding officer of a ship or unit rather than their actual rank. The term "Captain" is a role that signifies authority and responsibility over a vessel, and it may be held by individuals who possess varying ranks, not just those who have attained the formal rank of Captain in the naval hierarchy.

For instance, a Lieutenant can serve as the captain of a smaller vessel, reflecting their assigned leadership position rather than implying that they hold the highest rank available. This title represents the leadership role and accountability that comes with commanding a ship or unit, which is crucial in naval operations for effective decision-making and execution of duties.