SAN DIEGO (Sept. 15, 2021) Sailors embarked with the Medical Treatment Facility's (MTF) Air Department aboard the Military Sealift Command (MSC) hospital ship USNS Mercy (T-AH 19) man a firehose during Mercy Exercise (MERCEX) 21-4 on the ship's flight deck Sept. 15, 2021. MERCEX 21-4 is a week-long, pierside training evolution that culminated in a capstone emergency scenario. Mercy can steam to assist anywhere to provide relief as a symbol of Navy Medicine’s abilities around the world, and must be in a five-day-activation status in order to support missions over the horizon, and be ready, reliable and resilient to support mission commanders. (U.S. Navy photo by Mass Communication Specialist 2nd Class Jake Greenberg)