Chief of the Boat
The Chief of the Boat, or CoB, of a starship (also known as the Command Chief or CC on starbases and colonies) is the most senior Chief Petty Officer (including Senior and Master Chiefs), regardless of rank. The COB/CC performs the following duties: serves as a liaison between the Commanding Officer (or Executive Officer) and the enlisted crewmen; ensures enlisted crews understand Command policies; advises the Commanding Officer and Executive Officer regarding enlisted morale, and evaluates the quality of noncommissioned officer leadership, management, and supervisory training.
While it is usually true that the CoB/CC is the most senior enlisted man, it is not strictly required. The commanding officer is neither required to select the highest ranking man or the most senior in time in grade aboard, nor to replace his CoB/CC with a more senior man who reports aboard after the COB's selection.
When a new enlisted crewman joins a vessel or facility's crew, the CoB/CC is usually one of the first people he will meet. While the CoB/CC is outside the direct chain of command for sailors junior to him, he has a tremendous amount of authority and carries a lot of weight, generally being thought of as the top of a virtual enlisted chain of command.
The CoB/CC works with the department heads, Chiefs, supervisors, and crewmen to insure discipline is equitably maintained, and the welfare, morale, and health needs of the enlisted personnel are met. The CoB/CC is qualified to temporarily act as Commanding or Executive Officer if so ordered.
NOTE: Warrant Officers (Including Chief Warrant Officers) do not hold the CoB position. They have been commissioned by the President of the United Federation of Planets and are no longer technically enlisted; even though they share many characteristics with enlisted personnel, such as their specialized nature.