A Senior Enlisted Advisor (SEA) in the United States Armed Forces is the most senior enlisted service member in a unit, and acts as an advisor to the commanding officer. Formal, E-9 billets for the senior enlisted advisor are established at Service unit (e.g., battalion, wing or higher), command, major command, force or fleet levels to the SEAs/CSELs of DoD Agencies and the Senior Enlisted Advisor to the Chairman of the Joint Chiefs of Staff. SEAs are also known as Command Senior Enlisted Leaders (CSEL). Always a non-commissioned officer, the SEA is the main link between the commanding officer and the enlisted service members under his or her charge.